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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

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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

 

SSTV & FAX

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 :

 HF WEFAX SCHEDULES