FT736 and FT8

[Mark Spencer]

Hi sorry for the new thread.  I can't seem to be able to reply to existing ones from my phone..   Anyways I have made numerous FT8 contacts with my FT736 on 222 and 432.  

I'd be happy to chat off list with anyone who is intereard.    Am traveling today and expect to have some down time during my journey.

[Mark Spencer]

Hi here is a slightly changed version of what I sent Rod earlier today (I have had several off list inquiries re this.)  Sorry this is from memory and I didn't have any of the equipment in front of me as I typed this.  

As a general comment I don't run my FT736 much on 2M and I have never tried to use it with FT8 on 2M.   I doubt my very simple method for using my FT 736 with FT8 on 222 and 432 Mhz would work very well on 2M or 6M for those of you who have a 6M module. 

I also don't use any form of computer rig control (other than PTT.)  So I need to manually set the frequency on the FT736, and enter the frequency I am using in WSJT-x so any uploaded spots to PSK reporter show the correct frequency.   This may be an issue for some operators.

Sorry my solution is not a turn key COTS (commercial off the shelf) approach.   I suppose I went the COTS route later when I started using my Icom 7300 and 9700 on FT8, but the FT736 is still my goto solution for 222 Mhz FT8 and at times  I do sort of miss the non COTS approach that I use with the FT736.   (What can I say I like lots of cables, modules with connectors etc that can be repurposed for various uses over the years..)

That being said..

  With the FT736 and FT8 I keep things simple.   I apply TX audio to the FT736 from my  laptop headphone output thru the 1/8" Jack on the back of the radio (I think it is called the data Jack but may be miss remembering that) via an isolation transformer.   I did make a point of using well shielded silver Teflon coax for the connection from the isolation transformer to the FT736 as I was worried (perhaps un necessarily) about the signal quality in a roving environment.  I get RX Audio from the FT736 to the microphone input on my laptop by connecting to the terminals of an external speaker via a dropping resistor.   (An isolation transformer would probably be a good idea here as well.)   I adjust the volume control as needed to get a suitable signal level into WSJT-X.   I think the dropping resistor was several thousand ohms or more.

I use a simple home brew Serial to PTT interface connected to the PTT connection on the back of the radio (I think it needs to be grounded to put the radio into TX mode but may be miss remembering that.)   I believe the design uses transistors and was one of the typical circuits that was floating around approx on the internet for ham radio use approx. 10 years or so ago when I built it for another application (it fits inside a DB9 connector shell.)  

The manual for the FT736 should have details re the connector pinouts, signal levels, polarities etc.  I suggest any one planning on replicating my approach double check these details carefully in the manual and proceed at your own risk.

A few general comments.

In my experience my radio is stable enough (at least on 222 and occasionally on 432 Mhz) but some drift may be noted by others at times but qso's seemed to happen with out any real drama.    (I even once made a QSO using J65 (I think while using sub mode c ?) on 1296 Mhz without any real drama while roving from hill side vs staying at home in my radio room.)

The TX audio pass band isn't very flat and the power output will vary quite a bit as the TX audio frequency changes.   To be fair to Yeasu and the FT736 some of my older HF rigs of similar vintage from another manufacturer seemed to have a similar issue when I used them on HF with FT8 and other similar digital modes.    On 222 and 432 when running FT8 I typically pick a single spot in the pass band for my signals and don't change it.  If I do change my TX audio frequency I need to remember that the power level out of the FT736 may change.   The amps I typically use with my FT736 on 222 and 432 Mhz require full output from the FT736 for max power so I don't need to worry (much ?) about damaging my amplifiers if the power from the FT736 increases.  Those of you who may be relying on turning down the power from an FT736 to protect amps or other similar devices should consider this point carefully.

To mute the microphone I turn down the mic gain (otherwise ambient noise picked up by the microphone will be transmitted along with my FT8 signal.)

FT8 activity on 222 and 432 was sparse enough when I operated for me to be ok with those limitations.    I don't think I would be happy operating this way on 144 or 50 Mhz.   

A long time ago I used to use the FY736 for satellite work and had a different PC controlling the frequency for Doppler shift compensation but I haven't tried to get WSJT-x to control the radio.    Being able to run WSJT-x in "split mode" and have WSJT-X adjust the TX frequency would be nice but I haven't pursued that.   To recap I suspect operating on a busy band such as 2M without this functionality would be difficult.   

As usual the experiences of others may differ from mine.

I'm happy to answer additional questions off list to the extent that I can.

Hope this helps and good luck !

73

Mark S

VE7AFZ

[Ed Cole]

Very interesting, Mark.

My first venture into digital modes was running psk31 with a FT-847.
The interface was HB using a 2n2222 as keying transistor driven by
RS-232 DTR line. I found a couple small 600-ohm audio isolation
transformers at Radio Shack.

That interface was used for my initial use of JT44 and JT65 on 2m-eme
running early versions of WSJT.

In 2010 I decided to upgrade to a Elecraft K3 married with a DEMI 50w
144/28 transverter. The transverter was custom made for me with two
receiver boards so I could run both horz-polarity and Vert-pol
simultaneously for the new MAP65 program.

The K3 architecture dated from RS-232 era so my HB interface still
worked with it. It has internal audio isolation transformers so all
that was required was audio lines to the computer. Newer computer
doesn't have RS-232 so obtained RS-232/USB conversion cables. One very
nice feature of the K3 is Tx-Inhibit which holds off Tx RF until
activated by my sequencer.

Over time I acquired DEMI 222, 432, and 1296 transverters. All driven
by the K3.

I sold the FT-847 in 2012 but after a few years acquired a FT-736R with
144/432 only for a good price. Mainly needed a VHF-FM rig as the
transverters only covered 144-146 and 432-434. Being old it was a bit
clunky on memories and I/F for digital modes.

Last spring I impulsively bought a IC9700 to replace the FT-736R,
selling it to a ham here on the Kenai Peninsula for what I originally
paid for it. Also sold my 150w 2m amp to offset the cost of the new radio.

I'm very happy with the IC9700 which has 144, 432, 1296 bands all-mode.
I was pleasantly surprised to find Rx sensitivity equal to the FT-736R
(one of the great things about the FT-736R).

Have yet to get digital hooked up to the new radio. My K3 works fine
for that already so no great rush. I also bought the Bodnar frequency
reference board and PLL to improve freq. stability with an external
10-MHz reference (K3 and DEMI transverters already use the reference).

I run both FT8, JT65, Q65, and MSK144 with the K3. QRV only on 6m eme
at present (1000w Harris TV Amp and two 7-elem LFA yagis).

2m-eme array is slowly being rebuilt. 16-foot dish for 1296-eme still
waiting on welding shop to fabricated new dish mount.

No road trips for last two years due border closing (Covis-19).

73, Ed - KL7UW

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[Nick Krachmalnick]

Thanks very much for the information Mark,

I will puruse it carefully.

73 's and happy holidays to you and the family,

Nick

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[Roger - W7TZ]

I just put my 736R on the bench. I have a 6m module, a cw filter, and a pat board to install. This is a new used radio to me, though I've had it for nearly 3 years. I've had the top off once for a sneak peek and check the DC connector so I could build a source cable. AC power supply still works, and the radio works except the meter lights. When I pulled the bottom cover I was a bit taken back finding mouse excrement. Obviously a little cleaning is in order. And so I shall proceed.

73, Roger
W7TZ
CN83ia

Virus-free. www.avg.com

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