In reply to G4ERP:
Total weight is 36g but having just tried out
the VOX on the FT-817 for the first time I wonder if I need the PTT
switch. Does anyone use VOX during activations?
Hi Richard!
I have not used VOX, but it does occur to me that wind noise could trip the VOX in some weather conditions. I have often heard very loud wind noise on SOTA stations. Are you really going to lose much weight by removing the PTT switch?
73,
Walt (G3NYY)
In reply to G3NYY:
No experience of VOX on my 817 Richard. As Walt says you can often hear considerable wind noise on some activations and having been in some real houlies I’d prefer the backup option of a switch just in case.
Andy
MM0FMF
In reply to MM0FMF:
Hi.
Yes. Likewise very wary of VOX given the potential ambient noise level. As the FT-817 and 857 use the same mic arrangement, I can try it out before committing to removing the switch. The VOX certainly seems very consistent with a good threshold and immunity to false triggering just using the factory settings.
It might only be a few grammes saved but every little helps 
73, Richard
In reply to G4ERP:
It might only be a few grammes saved but every little helps
I’ve given up any concerns that I had about weight since changing from SLABs to LiPos. As far as I can ascertain there is a carrying threshold that my body works to which is around 11kg. Above that figure, the effort required to ascend a hill starts to increase, but below it the reverse is does not appear to be true, at least not until the load is so diminished that I am carrying my lunch and little more.
I recently changed from an FT-817 + linear combination to an FT-857 and removed no fewer than 12 plugs and sockets from the system, not counting those on the pieces of equipment themselves. That alone has saved a significant amount of weight as well as removing potential failure points from the system. I can’t however say that I am willing to take it one step further and remove weights from my microphones.
73, Gerald
In reply to G4OIG:
Good afternoon, Gerald.
I think there’s truth in your assertions but I suspect for a frequent activator, it’s more to do with being above or below one’s “normal” pack weight. In this particular case, I’m going to be above my normal weight and I’ll be stuck with it for over 100 miles so as I say, “every litle helps”.
Okay on the change to the FT-857. As you also say, a step up in reliability. Did you take my scribblings in the handbook to heart or was that before it was published?
73, Richard
In reply to G4ERP:
Okay on the change to the FT-857. Did you take my scribblings in the handbook to heart or was that before it was published?
I’m not sure what triggered the mood for change Richard - probably carting the 50W 70cms BNOS linear up Red Screes did it - not the weight issue, but the complexity of dealing with the equipment on the summit. It was a very sudden decision and it all came together very quickly when I realised I had a 736R growing mould on the shack bench… the bench itself isn’t that far behind! 
Actually talking of behinds… I realised that 99% of my QSOs over the past 4 years have been made with my behind on or close to the ground, so why have a rig wasting away in the shack when it could be p.ex’d against something much more useful. So the move to the 857 and the 817 is still available when I wish to go lightweight.
All the best for your 100 mile trek - as you say, in that case every little bit will help!
73, Gerald
In reply to G4OIG:
Having less cables to trip over and get broken has to be good news.
After adding some suitable decoupling at both LF and RF, I’m going to try the headset mic again tomorrow. That assumes the WX forecast doesn’t get worse - and if it does, I’ll probably nip back up onto Cleeve anyway at some point over the weekend.
I’ve had a few QSOs from home with it now so I think that just leaves the potential for RF feedback when sat directly under the antenna. If it passes the test with the FT-857’s QRO tomorrow, it should be okay with the FT-817.
73, Richard
In reply to G4ERP:
I hope the tests go okay Richard. I’ve still to sort out the RF feedback on my 857 when running 20W on 70cms, but it will probably have to wait until the better weather when I can spend time sitting on the lawn beneath the antenna. In the meantime I’ll be 3dB down. I had a similar issue on occasion with the 817 + linear on 70cms, but one that was subject to Murphy’s Law and so popped up only occasionally.
As for fewer cables in my installation, they were all inside a box inside the backpack so they weren’t an issue with regards to safety. The connection between the rig and mic + headphones is however something I’m quite keen to sort out and so I’m looking out for a bluetooth adaptor… hopefully once I’ve constructed a suitable bluetooth amplifier arrangement, I can get Paul to take my rig and antenna up the hills and stay at the car to operate. 
73, Gerald
In reply to G4OIG:
Afternoon.
What do you use for an antenna on 70cm - and probably more importantly how is it fed? I haven’t noticed any problem on 70cm with my FT-857 and I have it wound up to maximum. Maybe no one liked to tell me.
73, Richard
In reply to G4ERP:
Hi Richard,
I use either a DK7ZB dual-band or a DL6WU mono-band yagi. I have experienced feedback with both designs, though I suspect the choke balun feed on the dual bander is not right and I am going to try a smaller choke the next time I’m out. The DL6WU is gamma matched and has generally been less of a problem with the feedback being easy to eradicate usually by moving the coax. The problems have always been when I have sat beneath the antenna, which of course is usually the case so as to facilitate rotation. I think had you experienced feedback, then you’d have been told - politely of course!
73, Gerald
In reply to G4OIG:
… politely, of course. I’d rather know about it if I’ve got a problem.
FWIW I have always used 1/2wave coax baluns and folded dipoles on the hills, having had poor experiences of setting up gamma matches in the bad old days before things like the MFJ analyser came along.
73, Richard
In reply to G4ERP/G4OIG:
Just wondering what coax you chaps are using on 70cm?
At home I would not use anything less than RG213 and prefer Westflex 103, but on the hills it is impractical and use RG58 which is unbelievably lossy at 70cms. I would suspect a poor quality shield could be to blame for RF feed back, but I have had it were the outer braid became loose for the plug as well.
73 Steve GW7AAV (Who is probably preaching to the choir here)
In reply to GW7AAV:
Hi, Steve.
I use RG-400 with crimped connections - BNC at the bottom and SMA at the top. When I go walkabout I use RG-316 to save weight but then I don’t use 70cm and 2m is the highest band. It’s a bit lossy, but in that particular case, weight is everything.
73, Richard
In reply to G4ERP:
Hi Steve,
I use 5D-FB semi-rigid cable which I find far far easier to handle on a cold and windy summit than RG-58U. I have a 4.7m length with BNC’s fitted to both ends and a small RG-58U BNC to croc clips patch lead tail with the choke balun inline up to the antenna or I use a BNC to SMA patch lead for the DL6WU which has a Gamma match. I carry a RG-58U spare cable which has the balun inline, but will replace this with another 5D-FB run and separate balun in due course.
For a lazy day on the summits (International SOTA weekend, etc), I use LMR400 fitted with N types feeding a 15 over 15 on 23cms, otherwise it is just the toastrack on the end of a BNC to SMA patch lead with the toastrack held up in the air.
73, Gerald
P.S. You have a point about leakage from RG-58U on 70cms - I was using the spare lead when I had my feedback problems. I think that second run of 5D-FB is imminent!
It took a while but I think I finally got there and now have a lightweight headset that works with the FT-817. Thanks everyone for putting up with the intermediate attempts and thanks for the nice comments on the audio today. It was slightly more of a challenge than I expected.
Briefly, it is based on a Hi-Tex BEP-55NC electret (condensor) noise-cancelling microphone from Maplins. There are three key points.
The weight? 36g. That’s a bit lighter than the 170g of the standard Yaesu MH-31 mic. It will be going with me on my re-scheduled South Downs Way trip in a couple of weeks.
73, Richard
In reply to G4ERP:
Is the circuit diagram available somewhere please?
Also, on his site (PY1AHD ALEX - Alexandre Grimberg - py1ahd), PY1AHD talks about “adjust the microphone and the vox gain on the FT 817 to compensate the differences between the microphone manufacturers” did you try this, his circuit seems simpler than yours and I wondered if these adjustments allow the simpler circuit?
Colin G8TMV
In reply to G8TMV:
Surly that is only necessary if you wish to use Vox? I hate vox with a vengeance due to a couple of dumb locals one of whom who over the years transmitted his domestic fights over the calling frequency on two metres and another who blocked the same frequency with a ticking grandfather clock close to his rig for months on end.
Steve
In reply to GW7AAV:
PY1AHD is talking about adjusting the Microphone Gain (as well as the vox gain) to correct for the different type of mic since different mics have different output levels.
