Zycomm FM5016 VHF mobile transceivers

[Robinski65]

Recently we were given some old Zycomm FM5016 VHF mobile transceivers. As radio amateurs, we were hoping to convert them to work on the 144Mhz 2m band.

Unfortunately, we have been unable to find any information whatsoever about the radio from the Internet. I have also tried to emailing Zycomm Sales and Tech Support, but received no replies – not even automated responses.

Does anybody have any information such as schematic, programming details etc. That you could send us?

G4XRA

[Jon_G4MDC]

Not sure Zycomm manufactured any sets. I suspect they badged someone else's.

Pictures might help identify. If you can show the PCB then at least the method of programming should be apparent uP, EPROM, Diode Matrix etc.
Presumably they are not old enough to be crystal controlled.

[SiriusHardware]

A very quick look found this very old thread on another forum, which would seem to suggest that the frequency programming is generated by a specific DOS program and held in a 27C32 EPROM.

https://uk.radio.amateur.narkive.com/U3zFWU0D/zycomm-5016

The respondent in that thread, G7NPW, may still be around and may even also be a member of this forum, possibly.

[Jon_G4MDC]

That defines the generation then. It's probably not rocket science and a download of the original proms would likely enable the data to be reverse engineered.
If it is uP based the checksums might need to be worked out. If it is like the MX294 then it is just a table addressed by the channel switch and read by the synthesiser but the byte ordering is weird in that one.

[Terry_VK5TM]

G7NPW's contact details are here https://www.derby-radio.co.uk/contactme.htm

[G6Tanuki]

Zycomm were very closely associated with Lowe Electronics, from memory G3ZYC took over a slice of the company when Bill Lowe sold up. Lowe were Trio importers, essentially the UK representative for Trio-Kenwood back then, which would make me think that perhaps your Zycomm radio has underlying commonality with some of the TK series of two way gear from Trio-Kenwood.

[SiriusHardware]

If Robinski65 is able to read the original EPROM, post its contents as a .bin file contained in a .zip file and state the TX frequencies of the existing programmed channels, plus details of any synthesiser IC types and the frequencies of any crystals and crystal or ceramic filters found in the set maybe we can work it out.

[Robinski65]

Hi Guys
Thanks for the responses

the set has a 2716 erpom and a motorola 145146 PLL forming the frequency sythesis sytem. (As far as i can work out). we managed to contact one of the original owners o Zycomm - who sold the company years ago, and had no info on it. But we are still working on some reverse engineering, but not got far yet

[Jon_G4MDC]

There is a bit more to know.. The small 8pin DIL near the crystal and trimmer (3rd photo) is probably the prescaler but it's not possible to read the type number.

[SiriusHardware]

Datasheet for the PLL IC (or equivalent) is here:

https://www.lansdale.com/datasheets/ml145146_rev0.pdf

Unfortunately it's not a simple byte-wide parallel code input interface as found on some other Motorola PLLs - looks like you have to feed it 8 x 4-bit values one after the other while advancing the values on the A0-A1-A2 pins of the PLL and latching the data into the PLL at each step.

This would most easily be done with a microprocessor / microcontroller but there may be a dedicated upcounter / loader circuit doing that job instead.

[SiriusHardware]

The chip above-right of the EPROM (image 2), is that an MC14161B? (last character of the IC number is obscured). If so it is a 4-bit counter, so most likely that will be being used to apply ascending binary values to the A0, A1 and A2 pins of both the PLL and the EPROM.

[Robinski65]

Hi Gents

Sorry to keep providing info in dribs and drabs

the chips are :

MC145146P-2

4-Bit data Bus input PLL Frequency Sythesizer

MC14161B

Synchronuous Presettable 4 Bit counter

TC4069

Hex CMOS buffer

uPD2716

16,384 bit Eprom

Thanks Robin

G4XRA

[Jon_G4MDC]

Sorry but that still misses out the prescaler.

It is the 8pin one marked, I think, as SP8793 or SP8795.

The difference between them is the division ratio which has to be known before any programming can be worked out.

[SiriusHardware]

Robinski65, as well as the number Jon has asked for it would also be helpful if you can read the frequencies off any filters and crystals which you can see in the set, although I think I noticed a 21.6 (?) MHz filter in one of your earlier photos which would tend to suggest that that that is the first receiver I.F frequency. (If so, quite unusual - 21.4 MHz would be more common).

Also a readout of the code currently in the EPROM along with a list of the currently programmed TX frequencies would be very useful as that would allow us to verify any theories we may have about how the programming goes.

[Robinski65]

Hi - sorry missed that one before

it's marked as follows:


PS SR
SP8793
8346A


So a SP8793 ?

Thanks

Robin

[Robinski65]

A better shot of the frequency sythesizer

[SiriusHardware]

I'm actually wondering if that add-on bodge is a CTCSS generating unit - it may be rigged to modulate the VCO with a low level of low frequency audio in TX mode only. In that case the DIP switch would be for selection of the CTCSS frequency.

Aha, it is, look at this:

https://www.com-spec.com/atncht.htm

The 'IC-107' is referenced near the bottom of that page. This will actually make it more useful for amateur radio in the long run, but I think we can discount that small PCB and the ICs on it from having anything to do with the main frequency synthesis circuit- other than it probably injects low frequency modulation onto the VCO in TX mode.

[SiriusHardware]

Incidentally just doing a net search on 21.6MHz throws up quite a few RF filters with that centre frequency so I think that probably really is the receiver 1st I.F frequency.

[Jon_G4MDC]

Thanks for info about pre-scaler. SP8793 it is then.
I think I have some gen on that com spec CTCSS board. Will look.

Ah - and we need the synthesiser reference crystal frequency please. 12.8 or 6.4 MHz others are possible...
It is the one with two resistors kludged to it with silicon goo.

Actually there is another crystal on the RX board which would settle Graham's question about 21.4MHz or 21.6MHz IF if the frequency can be read please.

[Robinski65]

Originally Posted by SiriusHardware

I'm actually wondering if that add-on bodge is a CTCSS generating unit - it may be rigged to modulate the VCO with a low level of low frequency audio in TX mode only. In that case the DIP switch would be for selection of the CTCSS frequency.

Aha, it is, look at this:

https://www.com-spec.com/atncht.htm

The 'IC-107' is referenced near the bottom of that page. This will actually make it more useful for amateur radio in the long run, but I think we can discount that small PCB and the ICs on it from having anything to do with the main frequency synthesis circuit- other than it probably injects low frequency modulation onto the VCO in TX mode.

Yes the cludged on board is for the CTCSS - found some info
here:

https://www.repeater-builder.com/com-spec/com-spec-index.html