THE ZZ "WAVE NET" ANTENNA BY VE6VIS

A DUAL LOOP - 80 AND 40 METER HF WIRE ANTENNA PROJECT
When you can't go out, you've gotta go up!
Updated Sept, 2006 with new information
Do you want a full wave loop for 80 and 40 meters but have only a city lot?
Got a 64 foot tower or equivilant support with enough space at the top to add some insulators and a little time plus some wire? Got some 16 foot supports for each end? Want a great signal on both bands?
Then try this antenna project submitted by Mike Wigle, VE6VIS and prepare for loads of fun!


This antenna is the result of many hours of thinking and tweeking and trial and error and starting again and again. It was worth all the effort as I have come up with a very fine antenna that should make the lives of many hams much better by using a loop antenna instead of the inverted V's that so many of us use now.
The antenna is basically a full wave 80 meter loop on top and a 40 meter loop on the bottom all supported from a 64 foot center support, namely my tower. They are both fed from the center feed point with one length of 50 ohm coax. No tuner is required. Use the standard formula: 1005/freqmhz, (your center frequency), for total length of each "loop". Adjust for best swr by raising or lowering feed point from top of antenna. It requires the 64 foot center support (tower or mast) and 2, 16 foot end supports. VE6VIS
Editors note:
Another way of looking at this project is that two Delta loops, one for each band and squashed to fit the space on the tower and your lot are paralleled and fed with one length of coax.

The ZZ Wave Net is a revolutionary
new design in HF antenna's.
The ZZ Wave Net starts with
the same principal as a dipole
antenna bent into an inverted V.

Next, the ZZ is a folded dipole bent
into an inverted V loop!!!

Next we pull the ends of the folded dipole and separate
the middle as in the drawing above.
This allows us to install the antenna in a city lot and still
keep the overall performance of a full wave loop antenna!

Then we add the 40 meter ZZ loop under the 80 and we have the ZZ Wave Net, a dual 40 & 80 meter full wave loop antenna!

Below is how it looks installed on a 64 foot tower with 16 foot
end supports on your city lot.

Dimensions:
(80 meter on top, 40 meter on bottom)

80 meter apex to end 70 feet/ 21 m
80 meter end to feedpoint 65 feet/ 19.5 m
40 meter feedpoint to end 36 feet/ 10.8 m
40 meter end to bottom 34 feet/ 10.2 m

Apex to feedpoint 24 feet/ 7.2 m
Feedpoint to bottom 12 feet/3.6 m

Feedpoint is 4:1 balun
Both loops feed from this point

End support to end support 105 feet/ 31.5 m

Construction:
Measure wire and lay out at base of tower.
Attach 1 litre bottle half full of water to the bottom wire about 12 feet from the ends on both sides of antenna.This is so the wires don't twist and so the antenna will have greater tuning range.
Attach apex of antenna to top of tower on a standoff and preferably with a rope and pulley system.
Pull feedpoint up to 24 feet below apex.
Pull ends out to look like the picture.

Tuning Instructions
The wire length is the first thing to get right.
Use the usual method of (low longer) ie: if the swr is higher on the low freq then make the antenna longer and if the swr is higher on the high side then make the antenna shorter.
Then the next step is the distance between the wires.
The distance between the feed point and the apex is 24 feet @ 80 meters.
The final tuning is done by tightening the wires from the ends.

Tight ZZ


So you get the antenna pulled out to look like the
picture above, then you can adjust the swr by tightening and
loosening the wires. You will see a great range of
tuning here which is why this antenna design is so
easy to tune.

The best way to do this is to mark the place where the
rope meets the tie off point. ( this is the trick for
tuning this antenna) So, if for instance you have the
rope tied off to a tree. You mark the point where the
rope meets the tree by tying a piece of string onto the rope.
This is your marker.

Check the swr. Then loosen the rope so the marker is
about a foot from the tree, Then check the match again. You
will notice that it has changed. Now you can tune to a
point where the match is lowest.
Shorten and lengthen the wire to provide the lowest swr
within the range that you can loosen and tighten the wires
for lowest swr and you will find that this antenna will
match right down flat at the operating freq of your choice :)
Also you may find that the antenna wants to be shorter
than the normal calculation.This depends on a number of factors
like reflections and hieght above ground.

Tune the 80 meter length first and then the 40.
This antenna also works as an 80 and 20 or 80 stand alone,
40 stand alone, 40 and 20 etc.

Have fun :) Mike Wigle, VE6VIS
Russian Translation here
by UA3TJC

The EWE Antenna

VHF Magnetic Loop ON6MU

Antenna Trap WA7JHZ

80 METER FRAME ANTENNA

80 METER FRAME ANTENNA
by Harry Lythall - SM0VPO

http://web.telia.com/~u85920178/antennas/frameant.htm

I keep on and on about my little balcony and the antenna restrictions it imposes on my HF antennas. This projects was developed as a result of experiments to become QRV on 80 meters, again, using the little balcony. I have now built several of these antennas with equal success every time. The frame antenna may not be the most efficient but it can get you QRV on 80 and is ideal for boats and holidays. The VSWR is almost 1:1 from 3.5 to 3.8 MHz. The antenna may be modified for 1.8 MHz but the efficiency may suffer.

CONSTRUCTION

The construction of the antenna is shown above and is a five turn loop of one cable from 5 ampere mains cable. The cable must have a multi-stranded conductor. The antenna uses over 20 meters of the cable, so I stripped down 7 meters of 3-core cable and soldered the ends together. Construction is otherwise quite straight forward if you follow the above drawing. Note that all cable lengths shown are approximate.

The two boom poles - I have used both cane and a plastic clad tin (metalic) pipes, of the sort that are sold in garden shops. Both worked very well in spite of the difference in materials. If you do use metal booms then insert some form of insulation in the holes before you pass wire through them. I used plastic drinking straws from MacDonalds. This will prevent the metal from digging into the cable insulation, as well as improving the insulation.

With the dimensions shown each loop will be separated by 4cm. The natural capacity between the turns will tune the antenna to (about) 4.15 MHz, just above the 80 meter band. One of those Jackson 804 / 805 VHF tuning capacitors with about 25pf will tune the antenna down to 3.45 - 3.90 MHz. The tuning capacitor MUST be one with a couple of millimeters between the plates. The antenna has a very high Q so the voltage across the capacitor will be very high, even with small QRP powers.

160 METERS

A capacitor of 410 pf placed across the tuning capacitor move the antenna frequency down to 1.9 MHz. This capacitor MUST be a high voltage type. This antenna could get you QRV on 160 meters although efficiency is likely to suffer, but Ok for local nets and the like.

TRIMMING

If the 80 meter antenna does not naturally fall on 4.15 MHz, or the tuning capacitor is not centered on the band then some frequency adjustment can be made to the final antenna.

If the frequency is a little LOW and you need to increase it then some of the self capacity must be removed. Thread a bit of plastic tube between the wires of one side; IN, OUT, IN, OUT, IN. See '*1' in FRAMEANT.GIF. Repeat on more than one side of the frame antenna if a larger frequency increase is required. If the increase is still not enough then insert two tubes in each side and slide them apart to get a large increase.

If the frequency is too HIGH and you need to decrease it then some more capacity must be added. Connect a high voltage capacitor across the variable tuning capacitor. A short length of coaxial cable is ideal. Cut the coaxial capacitor shorter to reduce to the required capacity (increase the frequency). Do not be tempted to make a 'gimmick' capacitor with two wires twisted together; it will burn, even with a couple of watts of RF. This means that you have added more losses.

Have fun, de HARRY, Upplands Vasby, Sweden,

Broadband Transformers plus Mixers

Broadband Transformers plus Mixers

There are 2 basic types of broadband transformers used in most QRP work, conventional and transmission line style. Both types can be wound on ferrite toroids, potcores or rods, however for this discussion we will confine ourselves to the toroidal types used to give a 4:1 impedance transformation. These transformers are used throughout the various projects on this website. For MF and HF uses, a ferrite core permeability of 850-900 is generally required and the FT37-43 ferrite core is suitable. This will allow AC circuits to transform from unbalanced 50 ohms impedance up to 200 ohms unbalanced impedance or visa-versa. Shown below are three equivalent schematics of the 4:1 transmission line transformer. The center drawing is the easiest to conventionalize, however close examination will show that all 3 schematics represent the same thing. The high impedance is 200 ohms and the low impedance is 50 ohms in all cases. It is important to know that these transformers are symmetrical and the points labeled Ground or VCC can be switched with the point labeled High Impedance. There are a great many published references on RF transformers for further study.

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Winding the 4:1 Transformers

These transformers are wound as bifilar (2 wires) which are generally twisted together. Winding these transformers is very easy. All that is required is two 7 to 8 inch pieces of #28 AWG enamel coated wire and an FT37-43 ferrite toroidal core. A vise, ruler and a brace and bit drill are also very useful. I got my brace and bit drill at a garage sale for two dollars. You need to twist the 2 pieces of wire together so that there is around 8-10 twists per inch in the wire. To do this, loosely twist the wires at one end so they are of equal length. Place the twisted ends in a vise about 1/4 inch. Next, place the free wire ends together in your brace and bit drill chuck (no drill bit) and tighten up the chuck so that the wires are held secure. The wires should be of equal length and tension. Start hand winding the drill to twist the wires together and every once and a while use the ruler to check how many twists are in a one inch space. When you get to 8-10 twists per inch you are done and can trim the very tips with a wire cutter in preparation for winding.
You generally need somewhere ~ 7 inches of wire for winding a complete transformer. Leaving a 1 inch lead, wind ten complete loops through the toroidal core leaving a small gap between the start and finish leads.
Untwist the leads a little so that you have 4 separate wires. One set of these wires wires will be called winding #1 and the other winding #2. You need to identify them and further break them into 1a, 1b and 2a and 2b. Generally I regard the the top two windings as A and the the bottom two wires B. Use whatever system works for you. Strip off all the enamel on all four leads and then get your ohm meter or better yet a beeping continuity tester. Start on one of the top (A) wires by connecting the ohmmeter or continuity beeper to it and then touch one of the bottom wires and then the other bottom wire. Whatever bottom wire shows continuity with the top wire should be marked along with the source top wire with paint, liquid paper or whatever you like. Designate the marked wire pair winding number 1. You can test for shorts as well, there should be no connection between wire set 1 and wire set 2 at all! So now you have two wires sets, winding set 1 is marked and winding set 2 is unmarked. The top two wires are arbitrarily labeled A and the bottom two wires are labeled B . Refer to the diagram above for clarification. Connect 1b to 2a and twist them together and then solder. Your transformer is done. It is really easy to make these things. More elaborate methods such as using 2 color wire and painting one wire maybe used. These transformers will also work if the wires are untwisted, when you twist them, 8-10 twists per inch is a guide only and is not critical. Never use bare wire for these transformers.

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Homebuilding Diode Ring Mixers

Discussion:

Homebuilt diode ring mixers are also easy to make and can be quite a cost savings. A doubly-balanced diode ring mixer has two unbalanced to balanced transformers and a diode ring. The impedances at the three ports is 50 ohms. The transformers are wound with #28 AWG enamel coated wire on a FT37-43 ferrite toroidal core using a trifilar (three wire) technique. The wire twisting and winding technique is done as described above for the bifilar transformers. The connections 2b and 3a are twisted together and soldered. Again you will have to develop a technique to help you distinguish the wires from one another.

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Diodes

Discussion:

For optimal results Schottky or Hot-Carrier diodes should be used. However, common diodes such as the 1N914, 1N4148 or 1N4454 are all quite suitable and are much cheaper. The four ring diodes should be matched to help mixer balance and thus carrier suppression. At MF and HF the most critical matching required is the forward voltage drop across the diode and this is easily performed with a sensitive voltmeter. Set your voltmeter on the 2 volt scale to give you three decimal places for matching the voltage drops. Try and find 4 diodes close to one another. In addition, best results maybe obtained if all the diodes are the same type (ie. all 1N4148) and if they are all from the same manufacturer. Below is a easy schematic for matching your diodes with a voltmeter. Give the diode under test at least 20 seconds to warm up and stabilize before taking your voltage measurement.

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VE7BPO

Ladder Crystal Filter Design

John Hardcastle, G3JIR, described an interesting ladder filter design technique in 1980 that appears to have been forgotten. I've extracted the relevant information from John's article and presented it, somewhat simplified, in 'cookbook' form.

Basically, G3JIR's technique involves measuring the bandwidth of a simple two-pole filter, modifying it for the desired bandwidth, and then calculating the shunt capacitors required for a filter of the same bandwidth, but with more crystals to improve the shape factor.

The following test rig needs to be constructed. I just wired it up on a scrap of PCB material. Since the input and output impedance should be equal I used a dual pot. Separate ten-turn pots might make the settings easier if you want to get the resistance settings 'spot-on'. They aren't all that critical.

1. Using

               R1 = 0.613*1E6/(2*PI*f*C1) 

calculate the test impedance (Ohms).

2. Set the filter input and output impedance on the test rig to this value, measuring between A-B and C-D using a DVM.

3. Sweep the signal generator across the filter pass-band. The ripple should be about 1 dB with two peaks. If it isn't you've either got the calculation wrong, or set the pots incorrectly.

4. Measure the 3 dB bandwidth (BW1).

5. Calculate C for the desired bandwidth (BW2), using

               C2 = C1*(BW1/BW2)^2. 

6. Calculate the new impedance using

               R2 = 0.613*1E6/(2*PI*f*C2) 

7. Change the coupling capacitors to C2, and set the input and output impedance to R2.

8. Measure the new bandwidth. It should now be BW2.

To be continued ...

References:

Hardcastle, J.A. Ladder Crystal Filter Design. QST. November 1980. Pages 20-23.

Crystal Filter 9 Mc

Modifications for the Kenwood TH-78

Basics of modifying the Kenwood TH-78a


To open the radio, follow the instructions on page 64 of the manual.
(Unscrew four screws and break apart the radio halves.) The two TX/RX busy indicators (LEDs) have rubber seals placed over them. These have a tendency to fall off when opening or closing the radio.

All position references in this document assume that you are looking at the CPU board with the rotary encoders and TX/RX busy indicators at the top.
If you have installed the ME-1 EEPROM, I recommend that you temporarily remove it to facilitate access to the diodes.

You'll see a brass shield about one centimeter square covering the processor chip and the surface-mount diodes on the back half of the radio.
De-solder the shield's four corners and remove it. (I used an right angle surgical tweezers in conjunction with the pin-point soldering iron to lift the brass shield.)

Uncovered are the processor (which we ignore) and six surface-mount diodes, numbered sequentially from one through six (D1 - D6), top to bottom. These are about one millimeter wide; remember the note about skill and finesse.
New model radios also have two large loops of green wire, numbered one through two (W1 - W2), bottom to top.

You'll need a pinpoint-tip soldering iron and some braid to wick away the solder before you lift out the diode. Alternatively, Rich Garcia (n2czf@wt3v.nj.usa) suggests leaving the diode in place. "I found if you BRIEFLY touch the iron to the right side lead while gently pulling up on the SMC diode it should completely come off without needing to apply heat to the other side and further risk board damage."

After you perform some or all of the mods listed below, replace the brass shield and re-assemble the radio. Then reset the processor (as documented) and re-enter any frequencies into memory.
Potential case design flaw


In the course of performing mods on my Kenwood TH-78a dual band handheld, I've discovered a potential flaw in the case design. While handling my walkie one day (after the mods were done), the display went blank and I could not turn the radio back on. With the radio split in half again, I could turn the radio back on but discovered all the memories were erased. The cause turned out to be some component pins on the front face coming in contact with the square bodies of the two volume/channel/squelch switches, when the case is screwed back together snuggly. I placed small strips of electrical tape on the sides of the switches to insulate, and reassembled; problem solved. Now I have to reprogram the darn thing....
molson@bml4380.cpg.cdc.com (Mark Olson) said:

There is a warning on some of the rig mod bulletin boards about this. The problem is that pins on the back side of the PCB that is mounted on the front half of the TH78 can come into contact with the volume control housings mounted on the PCB on the other half of the unit. My radio had this problem until I put electrical tape across these housings. Symptoms were: Display blanking momentarily and the unit power cycling, sometimes causing memory erase, when pressure was applied to the front of the unit or to the volume controls. I originally thought that it was a loose battery connection...

Open up the radio and you will see what I mean... Believe me, the fix is simple and it works.
C-17 design flaw


William_A._Kirsanoff@smtpgty.anatcp.rockwell.COM said:

"The 78A WILL lose C-17 on the control board if dropped, period. This causes loss on receive audio on the left-hand side of the radio. The solder pads for that cap are not big enough. If you find the need to replace C-17, use a gap-fill cyanoacrylate glue like Zap-A-Gap (tm) to increase the device footprint. I have learned the hard way.
Otherwise, I have found it to be a fine radio. My only problems have been related to the C-17 issue and attempts to rectify it. Had I been given the above advice, it would have been a one-time only issue. As it is, I took out one of the microprocessors yesterday looking for a bad solder joint that was induced by my attempt to solve the C-17 problem (sigh). This radio gets a lot of use and a lot of travel. C-17 is the only thing that I have broken with the case closed.
Mutually exclusive mods


Some of these mods are reputed to be mutually exclusive. You must choose one of the following levels of performance:

The "beyond MARS" mod - gets you the widest tx/rx
The "MARS/CAPS" mod - halfway there
The "extended receive" mod - more of a good thing

plus

The "cross-band repeat" mod - a repeater that weighs almost nothing
There is no mods that manipulate diodes D1 or D2 (I've seen it suggested elsewhere that this is toggles the USA/Europe-ness).

Brendan_Hoar@notes.pw.com suggests:

"I think removal of D1 causes "Forced Channelized Mode", at least on the "new" radios. If you put both VHF and UHF memories into a TH78A without D1 and power on, you are stuck in channel mode until you do a full memory reset. Remember, you can't add frequencies or do any tuning in channel mode.

If you think about it, you'll want to be very careful not to let D1's circut become an open circut.
The beyond MARS mod


This mod provides the widest possible range of tx/rx. The mother of all TH-78a mods.

To mod (early model): remove diode D5 only.

To mod (late model): remove diode D3 and cut wire W1. D5 has priority over D3, so if you've already made the mods for the old model (which included the removal of D5) you must resolder D3 into D5.

Yields RX 50-179.995, TX 136-179.995, RX 300-399.995, RX 400-511.995, TX 400-511.995, RX 800-999.995.

To use: buttons operate the same way as described in the "extended receive" mod, except that you can transmit on a much wider range.

NOTE TO ALL: I haven't been able to verify the actual operation of my radio on all these freqs. Kenwood talks about the difference between the "dialable" range and the operating range. I'd like to come up with a chart for each level of mod that combines the above and the two following offerings. Help me, please.

* * * * * * * * * * * * * * * * * * * * * * * * * * * *

        Left VFO                        Right VFO

50.000-85.2x (with beep)                50.000-110.xxx (with beep)

85.2x-179.995                   110.xxx-179.995

300.00-399.975

400.000-511.9875                400.000-511.9875

                                800.00-999.9875

* * * * * * * * * * * * * * * * * * * * * * * * * * * *

Receive                         Transmit

---------------                 ---------------

50-135.995 (AM)        VHF      (NA)

136-179.995             "       136-179.995

300-399 (AM & FM)       "       (NA)

400-511.99           SUB-UHF    400-511.99

400-511.99             UHF      400-511.99

900-949.9875            "       (NA)

50-179.995 (FM)      SUB-VHF    136-179.995

The CAP/MARS mod


This doesn't cover as much room as the beyond MARS mod does, but may be more appropriate for those who use the CAP or MARS frequencies.

To mod (both early and late models): remove D6 only.

Yields RX 118-173.995, TX 142-151.995, RX 400-511.995, TX 425-454.995.
The extended receive mod


This is the mod that's usually given to hams to pacify them (the beyond MARS mod is closely guarded).

To mod (both early and late models): remove diode D5.

To use: press "F" for one second and then pressing the Band button will switch the UHF VFO to a 800-999.995 MHz band and the VHF VFO to a 300-399.995 MHz band. The regular VHF VFO can now receive down to 50 Mhz.
The cross-band repeat mod


To mod: remove diode D4.

To use: press "F" for one second, then "0". Repeat to disable. The MHz dot will flash when in repeater mode.
Toggle SHIFT button function


Press SHIFT during power-up This is described in the manual, but the documentation is not complete. The TH-78A can operate in two modes: In SPLIT mode, non-standard offsets (i.e. split frequencies) are supported, but the default offset is not programmable. In SHIFT mode, non-standard offsets are not allowed, but the default offset is programmable. To select the default offset, press F for 1 second, then SHIFT. See p. 30 of the manual for details on changing the default offset.
Toggle CALL button function


Press CALL during power-up. The CALL button can operate in one of two modes. In the default mode (CALLSW), it switches between the call channel and the last memory channel (if in memory recall mode) or last frequency (if in VFO mode).
After toggling the CALL button functionality (VMC), it will switch from the VFO to the last memory channel and then back to the CALL channel.
Observations on post-mod performance


Rich Garcia (n2czf@wt3v.nj.usa) observes "all original functions have maintained the same which is great. Aircraft band which was accessible before the mod remains with the same characteristics. It seems that VHF-High band has improved a bit on sensivity where it was dead as a dog before the mod (above 155.000MHz) but the 162.000 MHz band where weather radio is is still a bit deaf for reception at any distance but about 20 Miles. This depends on your (or my) terrain and transmitter output power.

"On UHF all public safety frequencies up to about 500 MHz seem to come in well but sensivity greatly drops from there (we really can't ask for more).
Frequencies can be programed in up to the 920MHz ham band but I have no way of measuring sensivity. 800MHz works but the signals are very weak, you must be near the transmitter for reception. Assuming you are in the town or city where the transmissions originate it should work.

"Transmit is enabled up to and incl. 500MHz but after testing this on a frequency counter I find that a signal is only generated to about 490 MHz, even though the trans. LED shows output in the higher frequencies.

"Crossband repeat seems to work fine but the audio is unacceptable for use, BE AWARE the radio gets HOT! Prolonged use or use on a busy frequency would not be recommended. Also remember this is a dual band HT please use a proper antenna while in this mode to avoid a high SWR, we should all know better... Right?"

Someone else said:

"I found that marine weather reports at 162.40MHz in my area were received much better on the SUB-VHF band, than on the VHF band...

"If you are having problems with intermod, try switching bands (i.e. using the SUB-VHF band rather than the VHF band.)"
Cloning


The TH-78a's memory can be copied from one TH-78a to another TH-78a entirely through radio waves "over the air" (i.e. without cables or other special equipment). Theoretically, this could be done via repeaters, although I've never heard it done. Allegedly this requires a mod that includes removal of D5 or D6, but I haven't researched it.

Cloning is a real boon to groups that want a bunch of radios to contain the same memories, such as amateur radio clubs, search and rescue units, and people too lazy to program their radios. Of course, given that the ME-1 memory expansion unit has 250 memories, laziness is understandable :-)

1. Set both radios to the same frequency.
2. Activate both radios by pressing the '0' key while turning the power on. The radios will display the word "clone".
3. Now, click the PTT button of the "master" radio. The radio will transmit in the economy low power mode. This may take about 4 minutes for fifty channels, or 20 minutes for the 250-memory ME-1. When the data has been transferred, both radios will revert back to their original frequency.
   (It is recommended that a dummy load be used to prevent unwanted interference.)
4. Turn both radios off and then on again. The slave is now a mirror-image of the master radio.

Cellular Telephones


Cellular phones operate at (tx) 824.040 - 848.970 (rx) 869.040 - 893.970, within reach of your modified TH-78a. The increments are, however, every 30kHz; the TH-78a will only increment in 25kHz steps at this frequency range, so the exact cellular frequency cannot be tuned in (most of the time).
Battery life on the TH-78A


wd6cmu@netcom.com (Eric Williams) says:

Some people have complained about the battery life on the TH-78A. I came up with these tips by checking out the power consumption under various configurations. In the case of power-saver mode, figuring out the average current with my DVM was impossible, so I ran the radio on a large capacitor and timed how long it took to die. These tips won't solve everything, but they might help.

The rig draws close to 2ma even with the power turned off, so don't leave the rig off with the battery installed for several days and expect full capacity to be maintained.

If you're only using one of the bands, shut down the other to extend your battery's life -- current consumption with the squelch closed is cut by almost a third.

If you're monitoring two frequencies on the same band, use the f2 button to receive both simultaneously rather than scanning between them -- the battery saver with two receivers will use about half the current of one receiver that is scanning.

You can make up a battery pack by putting nickel metal hydride AA cells in a BT-8 battery holder. A small strip of aluminum from the positive battery terminal to the depression in the top of the case will allow you to recharge the pack inside the rig. This will give you 1000mah capacity without enlarging the size of the radio, and NiMH cells have no memory effect. (But they *are* expensive.)
Game Mode


aviator@athena.mit.edu (who no longer exists), who credits
james@brokaw.lcs.mit.edu for "much of this".
To enter the game mode press M and PTT during power-up. Be careful not to accidentally reset the memory, which happens with M + power-up. (Don't freak; you'll see the same "all screen items lit" when entering game mode as when you reset memory.) To exit the game mode at any time, press the LAMP key. The volume, lamp, or frequency settings can't be changed while in game mode.

The top part of the display will show "H.00", which represents the high score. The lower part shows a scrolling message, "PRESS ANY KEY". Pushing any key starts a "Follow Simon" type game. The display will briefly show one of the characters '1', '2', '3', or 'F'. Press the corresponding key. The game consists of repeating the displayed character sequence, which increases by one character each round.

After you "win" the Simon memory game by getting correctly entering a sequence of twenty characters, the next game is a draw poker game.

The way it works is that you choose your bet (from 1 to 10) by pressing '2' to increment the bet and '5' to decrement the bet. Then, press 'F' to deal the five cards. The face value of the cards is displayed, and the suits can be seen at any time by holding down the PTT key. Any number of cards may be discarded, and to select (or deselect) a card for discarding, press the keys '1', '2', '3', '4', or '5'. If a card is selected for discard, it is displayed "face-down".

Press 'F' again to draw new cards. Your new cards will be displayed, and then if your hand is 2-pair or better, the screen will show the rank of your hand on the left (2P for 2-pair, 4K for four-of-a-kind, etc.). On the right the pay-off for that hand will be displayed. Your bet is multiplied by the pay-off factor,and the resulting pile of cash is displayed in the right hand side of the upper screen. (The left-hand side of the upper screen contains your table stakes, which are initially 100 coins from winning the Simon game.)

If you win the poker hand, pressing any key steps into the next stage. If you lose the poker hand, your bet is deducted from your stakes and you are asked to start another poker hand. In the next stage, you are asked "TRYB/S" which means, "Do you want to try double-or-nothing in a guessing game for Big or Small cards?" Press 'F' for yes, press TONE for no. If you say no, your winnings are credited into your stakes and you are asked to start another poker hand. If you say yes, then a single shuffling/incrementing card is displayed on the left, and three stars are displayed on the right. You have to choose to go for either BIG or SMALL, by pressing '2' or '5'. You can keep pressing '2' and '5' to change your mind. When you are ready, you must try to hit the 'F' key to stop the rotating card display, and the card will show, and you will either win, lose, or draw. If you draw, you have to play big/small again, I think. If you lose, your winnings are gone and you can play poker again. If you win, your winnings double and you are asked whether you want to play big/small again.

The payoffs on the poker are set against you, odds-wise; the double-or-nothing game includes a draw, so the odds are against the player there unless you can time hitting the 'F' key to win more than half the rounds. I haven't managed to do this, so I don't know if there is anything beyond this, all I know is that when the table stakes are exhausted, you go back to playing Simon again.
TH-78 - antenna hints


Hello everybody! Recently I decided to check the performances of small "Duckie" antenna specified as T90-0444-XX in TH78 manual.
I found that on 2 mtrs band this antenna, at first, has quite narrow bandwidth and, at second, tuned about 144.000 MHz or even some lower ( at the same time 70cm bandwidth seems to be enough...).
Because of "integrated design" of this antenna it would be nonsence to cut the top end, so I tried to find another way to tune it to the middle of 2m band. At last, the problem has been successfully solved! So, you can easy tune the central frequency up to 147 MHz - just place a copper ring in the middle of conical surface of antenna ( between "OO"s as shown below ):

  +---------------¾---

  |--  |          |     +-----------------------------+

  |--  | K E N W O|O D   | dual band antenna           |)

  |--  |          |     /+-----------------------------+

  +------------------/

               copper ring (about 13 mm internal diameter)

The ring made of 0.3 mm wire gave me frequency shift from 144 to 145 MHz; if you need higher frequency, you should use wider ring ( about 4...5 mm for 147 MHz ) - you can solder it of thin copper.
Don't use SWR meter for tuning! The best device is scanning scope or, at least, simplest RF field meter and your HT as VHF generator.

TH-78A (U.S.A. version) --> TH78E (European version) MODS.

If you bought a TH78A in the USA you don't have the 1750 Hz repeater tone access, but you can change that !

Apart from the well-known six diodes, the new CPU has 2 green wires.

In order to use the TH78A in EU, you must do the following:

1. First you have to remove D2 for the standard EU bands (144-146 and 430-440 MHz).
2. Now control that the 2 green wires and the 5 other diodes are installed (D1, D3, D4, D5 and D6).
3. If you need band expantion and components location, please see the mods below.

Although the TH78A has a special bandpass filter for the US 70cm band, I could not notice a decrease in sensitivity in the EU part of the 70 cm band.

There is a function change for 3 knobs; please see below and also p. 6 and 7 of your INSTRUCTION MANUAL.

    TH-78A   -->   TH-78E

    ---------------------------

    LAMP     -->   TONE 1750 Hz

    CALL     -->   LAMP

    TONE     -->   CALL

Now, you can choice between the CTCSS tones and the 1750 Hz with the following sequence: F + LAMP (the new TONE !) and then the right rotary encoder to make your frequency choice.
Crossband repeat, extended RX/TX


Owner assumes all responsibility for modifying or using these modifications!.

The following mods will provide for Crossband Repeat and extended receive and transmit on the Kenwood TH-78A HT.

I believe other functions are also enabled by these mods. which I have not found yet but I will update the file as news progresses.

Diode #4- Crossband Repeat
Diode #5- Extended Receive and out of band Transmit.

Remove all screws and open radio as explained in the Kenwood manual for installing the memory expansion module.
On the back cover you will find the memory expansion module socket and a copper shield to the upper left corner of it.
Under this shield their will be a row of SMC diodes which are unmarked in a vertical configuration to the lower right portion covered by the shield.

1. Remove the shield at its four corners with a solder sucker and SMALL! iron.
2. Carefully count down from the 1st diode in the row to the fourth one and remove for crossband repeat.
   HINT: I found if you BRIEFLY touch the iron to the right side lead while gently pulling up on the SMC diode it should completely come off without needing to apply heat to the other side and further risk board damage.
   I used a pair of right angle surgical tweezers for this.
3. Just as above you may remove the fifth diode to preform the extended receive and transmit modification.
4. Reset the CPU (yes you will loose all of your programed memories! argh!) by pressing Function for more than one second and then "0".
   YOU HAVE NOW COMPLETED THE MODIFICATIONS!
5. For 800Mhz go to the UHF band with the band switch and press Function for more than one second quickly following with a press of the Band switch again. 8---.-- will appear.
6. For 300MHz go to the VHF band and repeat as above. Original bands are restored by repeating the "F Band" sequence.

MY observations... All original functions have maintained the same which is great. Aircraft band which was accessible before the mod remains with the same characteristics. It seems that VHF-High band has improved a bit on sensivity where it was dead as a dog before the mod (above 155.000MHz) but the 162.000 MHz band where weather radio is is still a bit deaf for reception at any distance but about 20 Miles. This depends on your (or my) terrain and transmitter output power.

On UHF all public safety frequencies up to about 500 MHz seem to come in well but sensivity greatly drops from there (we really can't ask for more). Frequencies can be programed in up to the 920MHz ham band but I have no way of measuring sensivity. 800MHz works but the signals are very weak, you must be near the transmitter for reception. Assuming you are in the town or city where the transmissions originate it should work.

Transmit is enabled up to and incl. 500MHz but after testing this on a frequency counter I find that a signal is only generated to about 490 MHz, even though the trans. LED shows output in the higher frequencies.

Crossband repeat seems to work fine but the audio is unacceptable for use, BE AWARE the radio gets HOT! Prolonged use or use on a busy frequency would not be recommended. Also remember this is a dual band HT please use a proper antenna while in this mode to avoid a high SWR, we should all know better... Right?

After first booting up the CPU in the mod I found that the message screen showed "Cloning" so it seems that this radio now has cloning capabilities. After searching I have found that holding the "0" key and powering up the radio will display the clone feature, see below for further explination.This leads me to believe that this HT may have some more "Hidden" features that I am trying to find, some may be useful.

Thanks to Gary KC8UD who sent me the following via packet .....

CLONING:
The TH-78 can be cloned without cloning cables or special equipment. It is done entirely with RF, and, in fact, can be transmitted over the air, and even via repeaters. This may be extremely useful for those users who do not have the patience to program their own radios themselves. This application would also be useful for clubs and user groups. (However, this can take as long as 50 minutes with the ME-1 expansion module. It is recommended that a dummy load be used to prevent unwanted QRM.)

1. Both radios must be on the same frequency.
2. Activate both radios by pressing the "0" key while turning the power on. The radios will display CLONE.
3. Now, click the PTT of the "master" radio. The radio will transmit in the conomy low power mode. This may take about 4 minutes for fifty channels.
   hen the data has been transferred, both radios will revert back to the riginal frequency.
4. Turn both radios off and then on again. They will now operate normaly while the slave radio has the same memory contents as the master radio.

FREQUENCY EXPANSION

(1) You can receive from 340 - 399.987 Mhz FM by removing chip diode D8 on the ontrol unit. To access this function, press the [F] key for one second, and then the [LOW] key. This toggles between AMATEUR, AIR band (AM) and 360 Mhz.
AM and FM modes are selected automatically, depending on frequency.

** Since "F" for a second and "Low" toggles the power output, I wonder **

There is also a couple of arcade type games on the TH-78A. To start the game you pres and hold [PTT] and [M] keys while turning the unit on. The first game is a follow me type game. The radio beeps and shows a sequence of numbers flashing on the screen. You have to match the same sequence on the tone pad. Each time the sequence gets longer by one number. You have to keep remembering the sequence as one gets added each time. Once you get to a certain high score on that game, it breaks into a poker type game. To exit the game mode press the LAMP key at any time. The receiver still works in the game mode and you can adjust volume but no other features.

RG> The games seem to work fine and it is interesting that they have inserted that into the programing of the chips. Does anyone know of any further features in the radio be it games or radio functions.

PLL With HEP4059

7 Mc Spektrum JF1OZL

7MHz band monitor scope
I made a 7MHz band monitor scope. It exchanges all existing signals of that timing of 7MHz-band to viewer image like a hill on the oscilloscope . See fig5! It indicates what it makes. You know it in the catalog of IC780. ** See fig1! it indicates block diagram. See fig2! It indicates circuit. Saw signal-oscillator makes 11Hz saw signal. This signal controls VCO. VCO oscillates a signal changing from 17.6MHz to 17.7MHz ,repeating 11 times in one second. DBM changes 7MHz signal came from antenna to 10.6MHz IF-signal by mixing the 7MHz signal with 17.6MHz changing frequency local oscillated signal. Yes. This is basically same with normal single super heterodyne radio. But, instead of audio AMP, detected signal is inserted to vertical arc of oscilloscope. Saw signal is injected to a horizontal arc of oscillator. See fig4. It indicates that too fast sweeper make filter dull. This circuit is a type of spectrum analyzer. But vertical hight do not indicate logarithmic strength (dbV) but linear(V). I joint a dipole to this machine. This machine displays a view like fig3. I can know the opening frequency of 7MHz band. I can know where is jaming. I can enjoy to see this view.

3.5 Mc One Transistor FET Transceiver

VHF 30 W PA

HF 600 W Power PA

50 Mc FM Transceiver

VFO

100MHz Spectrum Analyzer

100MHz Spectrum Analyzer

Iulian Rosu, VA3IUL / YO3DAC

http://www.qsl.net/va3iul/

This Spectrum Analyzer supposes to be a cheap and a useful device for any ham radio. To build this device you need minimum test equipment, like a digital counter, an oscilloscope, Grid-meter and a multi-meter. The main design is based on SA605D, FM receiver from Philips. This circuit is very common in some old analog cell phones.
If we take a look to the main schematic, we can see that the input signal pass through a low-pass filter (L1, C2, C3), and it is amplified by a MMIC, MAR6, in order to boost the weak signal performance of the instrument.
It is important to remember never to exceed the maximum input level specification of the Spectrum Analyzer. Do not confuse the maximum input level specification with the 1dB-compression point or third-order intercept point specification. The maximum input level specification is the maximum input level that will not damage the amplifier or mixer. The 1dB compression point or third-order intercept point refers to distortion caused by excessive input levels. The third-order intercept point usually occurs about 10dB-15dB above the 1dB-compression point. If an analyzer specifies the 1dB-compression point as 0dBm, then input levels higher than 0dBm should not be present at the output of the RF attenuator. If the RF attenuation is set for 20dB, then the input level (at the input connector) may be as high as +20dBm without exceeding the 1dB-compression point. It is always best to allow an extra few decibels of safety margin. For example, if the 1dB-compression point is 0dBm, then the input level should be kept several decibels below this point for best performance.
If we check Minicircuits catalogue we can find that the 1 dB compression point for MAR6 is 2dBm with a gain of 20dB at 100MHz. But in the same time the SBL-1 mixer support on its RF input signals only up to 9dBm. So in our case, the limit of input signals will be around –10dBm, to keep a good linearity of our measurements.
The range of the VCO, used to down convert the signal to first IF, is from 150MHz to 250MHz. The VCO can use any NPN RF transistor, like BFY90, BFR90 etc. The varicap diode should be MV209 or an equivalent diode, which can give a good, voltage versus capacity linearity. L9 from the tank circuit has 3 turns, on 3mm diameter and 5mm length. With a frequency counter connected to pin 8 of SBL-1 you can measure and adjust the frequency range of the VCO.
On the output of the SBL-1 mixer, we have the first IF filter on 150MHz. The bandwidth of this filter is 1MHz. Each inductor of the filter has 5 turns, 1mm silver plated wire, on 8mm diameter and 10mm length. The trimmer capacitors (2-12pF) are used to tune the filter. Another MAR6 is used to amplify the first IF signal.
The circuit SA605D is a high performance monolithic FM system incorporating a mixer/oscillator, two limiting amplifiers, quadrature detector, logarithmic received signal strength indicator (RSSI).
The input match of SA605D is C9, C10 and L7. The tank circuit of the 139.3MHz LO (used to down convert the signal to second IF) is C12, C13, C15, L8. L8 has 6 turns, on 4mm diameter. Check for the right LO frequency on pin nr 4. For a better frequency stability you can use a 139.3MHz crystal oscillator. The second IF is 10.7MHz. I chose this frequency because here we can find plenty of IF filters. The main schematic use only one X-tal filter, which will give to the analyzer a 15kHz RBW (resolution bandwidth). Its possible to use here switched filters, for different RBW. For 3kHz RBW, is possible to use a SSB filter and for 150kHz RBW, ceramic filters used in broadcast FM radios.
One of the most important part of SA605D is the RSSI indicator, that will be our logarithmic detector. You can see the RSSI vs Input level graph in SA605D Datasheet and SA605D Application Note.
TL084(d), in a log amplifier configuration drive the Y input of the oscilloscope. The other 3 amps of TL084 (a, b, c) are used to generate the sweep signal. The output of (b) it will drive the X input of the oscilloscope.
This design expect to be a cheap Spectrum Analyzer, but in the same time with nice performances. For more improvements you can add a step attenuator, more poles to the front end low pass filter, switchable filters on 10.7MHz IF, a variable BW video amplifier for vertical output etc.

Iulian Rosu, VA3IUL / YO3DAC

Home http://www.qsl.net/va3iul/

Block Diagram

Low Noise VFO 5 Mc - 5.5 Mc

Mizuho MX21S Schematic

Generator 2 Mc - 12 mc

VFO 7 Mc - 7.3 Mc

VFO 5.5 Mc - 4 Mc