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Adding Extra Channels to a Tait T525 4M Transceiver

I have had a Tait t525 4m transceiver some time now and wanted to add extra channels.

I came across M1DYP Website showing me how to modify the Tait. So all credit goes to him.

The mod requires adding 2 DPDT switches to the front of the transceiver.This mod can be carried out on 2m &

70cm versions of the Tait T500 series transceivers.



The picture below shows the back of the switches.These are wired to the diode matrix.

 The diode matrix has diode links one for receive and one for transmit.

By choosing the correct diode links extra channels can be had .



Values of the diode matrix:

N1 - 500kHz etc
N0 - 250kHz                       

A5 - 200kHz
A4 - 100kHz
A3 - 50kHz
A2 - 25kHz
A1 - 12.5kHz
A0 - 6.25kHz
The above list has been corrected by Steve G4WWK ( Got the wrong list from a UHF T555 )

On channel 1 is on 70.450 mhz. This was not altered

On channel 2 is on 70.425 mhz. All switches taken off this matrix.


Left switch clicked down and channel 2 gives me  70.325 mhz.

Right switch clicked down and channel 2 gives me 70.4375 mhz.

Both switches down and channel 2 gives me 70.3375 mhz.

So by adding 2 switches i have ended up with 5 channels.

By adding another switch would give me even more channels. 


My thanks to Ken M1DYP for the idea.

M1DYP Website

 David Pye's Website


Yaesu MH-31 Microphone Mod

The Yaesu FT817D,FT857D AND FT897D are reasonable transceivers,but there is one area that is poor.

Namely  there is no Speech Processor.!

Yes the menu is there but no Speech Processor.

Most operators using SSB have to wind up the SSB Microphone level to close to 100 and shout .

Even then the transmitted audio is poor.

This is how this project came about and credit goes to M0UKD & M1GEO ( Links at the bottom of article )




For information on the MH31 Mod go to these links below .


M1GEO Website


 M0UKD Website

 Audio now is greatly improved .I will report more on the mod when i have had more contacts.

Anytone AT-588 Microphone Mod

This mod could also be carried out on the VHF & UHF versions of this rig although i have not tried it.

Only on the 4m version . The Anytone is also badged under TYT TH-9000,CRT-7M, POFUNG, BAEOFENG and a few other names



When i first got my 4m rig i was told my transmit audio was muffled and low.

While searching the internet for something else i can accross a mod for the same problem for the Leixen. VV-898.

 So armed with a screwdriver i took apart the Microphone.

 To undo the back of the microphone there are 3 screws.

Once inside you need to remove the circuit board. There are 5 silver screws holding the pcb and metal work.

With the PCB removed you need a drill with a 3.5mm drill bit fitted.

Carefully drill out the hole where the microphone insert sits.Clean off any burrs inside and out.


I reassembled inside the microphone but leaving out the silver screw in the middle of the silver metal spring plate.I put a piece of insulation tape between the silver metalwork of the PTT and the PCBto stop any shorts.

This is another known mod to improve the microphone. as if you lossen you grip on the PPT switch you will be unaware you have stopped transmitting, but the station the other ned will get chopped audio .

Like Norman Collier ?! . Check out the broken microphone sketch on youtube.

I did some on air tests through MB7FM the 4m parrot and the transmit audio was greatly improved.


As with any mods you do them at your own risk.


144mhz Transverter Attenuator


 This has been an interesting talking point at my local radio club (HARS ).

 My dad Les G6SXB and myself have used this as an attenuator for 10 years plus.

We have been told it is a filter.

It is interesting that it seems to work as either

Being tuned  as a filter or an attenuator.

I would be interested hearing from anyone  as this was a copy from Microwave Modules unit.

Transverter Attenuator for 28mhz Input Transverter



VHF / UHF Television Interference Filter Design


I set about building the filter and used a tobacco tin.

If you look in the picture i have soldered earth connections where the 75 ohm coax come into the tin.

Also soldered an earth near where the coils are soldered.

Each coil was wound around a drill bit to the size in G8MNY's paperwork.

Next each coil is soldered to a trimmer cap and then soldered to the tobacco tin.

Scrape the tin to ensure good soldered connection.

You will notice i have not used Polo mint size ferrite cores.Instead i have used clip on ferrites.

The filter below is made for 6m , 4m , 2m & 70cm.

Tune each coil on each band by adjusting the trimmer or opening and closing the coils.

If you run a preamp on your tv put the filter in before the preamp then adust.

I would be interested if anyone else has made one of these filters and how well it worked for them.   



Diplexer Project

A few months ago i brought myself a Yaesu FT8900 Quad Band Transceiver 10m, 6m, 2m & 70cm

While i was at it i purchased a Quad Band Antenna from Ebay.

On my car i use a roof bar to mount my antenna's.

This saves drilling the vehicle. [ SEE PICTURE]


I set up the FT8900 in the car and screwed the Quad Band antenna into the mount.

I did checks with my Revex W570 SWR/POWER Meter.

On 70cm all was ok with VSWR @ 1:5:1

On 2m VSWR was a little high @ 2:1

Next checked VSWR @ 6M & 10M. Things were not good @3:1


The roof bar is earthed out to the metal work inside the vehicle .

I tried adjustments to the Quad Band antenna, nothing seem to adjust.

I added extra earthing , still no joy. 

In desperation i changed the antenna to a 2m 5/8th wave whip.

Now for those who don't know a 2m 5/8th will work on 6m as a quarter wave.

VSWR on 6m now was a respectable 1:6:1 which i was ok with.

Now for 10m.I also had a CB Valour Half Breed which i had used on 10m in the past.

Again VSWR was ok @ around 1:4:1.


I concluded the antenna was either faulty or needed a lot more ground plane.

 I pondered on this for a few days and did some research on the internet.

My research came up with others having the same problem.


On doing my search i came across a website where a fellow Amateur had built a Diplexer.

The Diplexer worked on HF & 6M one side and 2m & 70cm the other.

This was what i needed. I checked the internet for a professional made Diplexer and price.

I found one the price was high at around £85 !

Hmm i looked at the diplexer project again and thought why not build one.


I studied the information and decided to go for it.

I have over the years played with EXPMR radio's and have a few scrap boards. 

I raided the boards for trimmers, sockets and bits. A mains back box was found for the box.

The only thing i needed was 3 yellow trimmers. I got these off Ebay.

As you can see in the picture the project came together very well.   



Tuning the Diplexer was fairly easy following the instructions.

On my first outing however problems struck. On chatting on GB3PE the receive signal disappeared.

On checking one of the trimmers it had melted.

I searched around and found a more heavier duty trimmer.It was a bit bigger.

So i altered the components around the board and readjusted the Diplexer.

This time i keyed the rig up on full power { 50w ) for 5 minutes into a dummy load.

No problems this time .

So now i can run about listening to 3 bands at once, 6m, 2m, 70cm.If i want 10m all i do is change the antenna.


 HB9ABX Diplexer



I have been interested in SSTV & FAX since i got interested in Radio.

Myself and my dad Les G6SXB had a great mentor. Richard Thurlow G3WW.Richard was one of the leading experimenters of SSTV at that time.


     This inspired us to try out SSTV. First of we used a Spacemark type SSTV unit and later a ZX 48k Spectrum.



                                   We then moved up market and brought a Wrasse SC1 SSTV Converter.




                                     Now days Les and myself are now using MMSSTV program.


                                                    Click on     MMSSTV Website


                                           The MMSSTV program is free to download and use.





                                                      Here are a few pictures Les has worked on HF









HF Weather FAX

 Radiofax, also known as HF FAX, radiofacsimile or weatherfax, is a means of broadcasting graphic weather maps and other graphic images via HF radio. HF radiofax is also known as WEFAX, although this term is generally used to refer to the reception of weather charts and imagery via satellite.


The program i use to decode HF Fax is FLDIGI. It is free to download .


 Click here for FLDIGI Download   




Tune frequency 1.9khz lower.


 Click on link below for :