Icom drops transmit after a few seconds - then "soundcard error"

1

TL;DR: When the FT8 program transmits, it stops after a second or two and has a sound card error,

I have an Icom 718 a buddy gave me when I got my general. I had been using it in digital mode with an MFJ 1204. The MFJ 1204 had seen better days, a cable broke. I managed to crimp a new end on the cable but decided to replace it. But it worked. This device acts internally as a VOX and then triggers PTT from the rear DIN plug. The MFJ shows to the computer as a sound card, speaker and microphone, and nothing else.

Yeah, that worked but I thought it was a little flaky. No reason. I was worried about the connector breaking off the wire again.

But had I bought a Xiegu G90 and the DR-19ā€¦and I discovered what rig control and split operation was like and decided I wanted to have those features on the Icom. All this was working and it was fun. This made me want to use JTDX with my HP laptop. I had successfully used it with the Xiegu and the MFJ.

So, based on all this, I bought a new Digirig Mobile with the cables for the 718, but it didnā€™t come with a USB C cable, just the 3.5mm for the cat cable and the DIN cable for audio and, because (I guess) the Icom does not do PTT via cat, I believe that the DIN also does PTT.

I found a C cable and plugged everything in and after some misunderstanding, got it working, after a fashion. The input side works, as decoding works, I hit transmit, a few seconds later, transmit stops and I get a ā€œsound card errorā€.

I do my setup, get the green when I test cat, and red when I test PTT, and the Radio shifts to transmit. Everything seems fine.

The transmit stops long before the transmit period is over.

SWR is under 2.

I thought it was possibly an RF hitting the USB cord issue. I thought that the USB was quality but I was unsure about the shielding of the wire - it was OK, but no ferrites. I wanted to be sure that it was not an RF hitting the USB cord issue so I purchased a Digirig brand USB C cord from Amazon. It had a ferrite on each end, and I figured that Digirig would have good shielding on a cable they sold.

So, same issue. I start JTDX. it listens and I see many decodes. I transmit. it transmits for 5 seconds or maybe 10, then it stops, I get an I/O error on the soundcard. JTDX wonā€™t recover after a sound card error unless I stop and start the program.

I thought the genuine digirig usb cable would fix things. Is this likely to be RF interference even with a properly shielded and ferrited cable?

2

Yes, most likely.

Try turning the rf output down on the radio itself.

If you can tx stable at ~5 watts, a deeper dive into rfi troubleshooting would be next.

:slight_smile:

Good luck
Kb0wlf

3

It is more stable at lower wattage, but it is not stable even at 20 watts.

The antenna I use is a Cobra Ultralite. I live in an HOA and while there is an Oak in the front yard and one in the back, I wanted to limit their ability to complain. The Cobra is a single wire to the front yard. That antenna uses 450 ohm ladder line and it uses a 4:1 balun to provide a uhf connector. A short length of coax to a commercial RF choke I bought (Amazon item B0D9NKKKCV) and then a longer length to an antenna tuner (the antenna seems to run at a high SWR intentionally, requires a tuner) and finally another short coax to the tranciever.

Where should I start?

4

i want to word this correctly in order to encourage and not discourage.

:slight_smile:

first, iā€™m not familiar with the cobra ultralite.
i understand the need to work within an HOA and applaud you for doing so rather than thinking a ham radio license negates any and all adult promises/contracts.
:wink:

the ladder line is next up. for current day operation, i would steer almost everyone away from ladder line.
ladder line is a great low loss feeder but modern coax and modern antenna design negate most benefits/use cases for the casual ham operator.

your icom, a good rig, has no antenna tuner.
(a matching device to match the output impedance of the radio to the impedance of the antenna SYSTEM)
so my guess is a good amount of reflected RF and a good amount of stray RF is knocking out your ā€˜chainā€™ from the pc to the radio.

the g90 has a great little antenna matcher in it and can ā€˜make upā€™ for a lot of antenna system issues. this does not make a problem antenna system work as good as a non problem antenna system though.

it it were me, i would run a good quality coax cable from the ic-718 to a wire dipole cut/tuned to the band youā€™re wanting to use (remember, no tuner in the 718) and see if that eliminates the problems.
another option is a half wave end fed with 49:1 unun.
also cut/tuned by hand.
also fed by a single run of quality coax.
the endfed would give you multiband operation but the wire element/radiator is ~65 feet long for a 40m-6m setup
(about half that if you go 20m-6m)

:slight_smile:
anyway, there might be a rearrangement of station equipment that reduces the rfi to pc/radio chain. as well as tuning the antenna system to create a good match to the 718 might clear things up.

my guess is changing out the antenna system.
(not what i would want to hear either)
:frowning:
good luck
kb0wlf

5

Between possibility of wired RFI (RF coming back from the antenna over shell of the coax) and wireless RFI (RF is induced from the power transmitted by the antenna) I would focus on wired first. Choking is one option. Hereā€™s Mike talking on the subject:

6

i googleized the cobra ultralite.

a G5RV style.
i thought that might be the case when you noted the ladder line.

for those antennae to radiate properly, the ladder line should be straight up an down and not near anything else.
the ladder line, in this type of antenna, is actually doing some ā€˜matchingā€™ depending on the band. the ability to match will be effected by any reflected rf from nearby obstructions/etc.

i ran a g5rv as my first antenna back in the early 90s but had room to stretch it out.
ladder line segment was ā€˜free hangingā€™.
the ic-736 tuned up just fine.
i moved to ladder line free installations within a couple years though.

good luck
kb0wlf

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