FT-857/897 deaf on 2m?

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FT-857/897 deaf on 2m?

Postby VK7HH » Fri Jan 04, 2019 10:32 pm

I have a FT-857 being used on my remote site using remote rig.

It *appears* that it's deaf, however it's a bit hit and miss.
I've done tests using WSPR with another station 180km who I regularly decode 10dB lower than he's receiving me. We are both running the same power.

Another test tonight, VK5's coming in on WSPR -

2019-01-04 09:30 VK5GF 144.490530 -26 0 PF94hk 20 VK7HH/P QE37ld 1082 141
2019-01-04 09:28 VK7HH/P 144.490500 +2 0 QE37ld 50 VK5GF PF94hk 1082 316

As can be seen 5GF spotted me at +2 and I received him at -26 and only running 3dB less power than myself. Obviously this could be all propagation related, however it seems to happen all too often. I've tested on local beacons and they seem fine.

The other potential issue it could be is noise on site or front end overload from nearby transmitters (there is multiple 865MHz TX about 5-10 metres away probably running 100W into a 6dB vertical + other TXs). Next step is a visit to the site to install a bandpass filter, but I thought I'd ask if anyone has seen similar performance with their 857/897.

Note I'm not running a preamp on the site and the antenna is a 8 element LFA yagi.

Regards
Hayden VK7HH
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Re: FT-857/897 deaf on 2m?

Postby VK4FP » Sat Jan 05, 2019 10:49 am

My FT857d had low sensitivity. Maybe yours has same issue. common Fault. In IF stage, Plenty of info on youtube how to repair .
However I may be wrong as you're using ssb for WSPR , not AM, FM modes of course . But a thought?

http://dh5ym.hopto.org/wiki/?p=766

Cheers,
Lloyd VK4FP /VK4TVL.
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Re: FT-857/897 deaf on 2m?

Postby VK4TI » Sat Jan 05, 2019 1:42 pm

"VK7HH"]I have a FT-857 being used on my remote site using remote rig.

It *appears* that it's deaf, however it's a bit hit and miss.
I've done tests using WSPR with another station 180km who I regularly decode 10dB lower than he's receiving me. We are both running the same power.

Another test tonight, VK5's coming in on WSPR -

2019-01-04 09:30 VK5GF 144.490530 -26 0 PF94hk 20 VK7HH/P QE37ld 1082 141
2019-01-04 09:28 VK7HH/P 144.490500 +2 0 QE37ld 50 VK5GF PF94hk 1082 316

As can be seen 5GF spotted me at +2 and I received him at -26 and only running 3dB less power than myself. Obviously this could be all propagation related, however it seems to happen all too often. I've tested on local beacons and they seem fine.

The other potential issue it could be is noise on site or front end overload from nearby transmitters (there is multiple 865MHz TX about 5-10 metres away probably running 100W into a 6dB vertical + other TXs). Next step is a visit to the site to install a bandpass filter, but I thought I'd ask if anyone has seen similar performance with their 857/897.

Note I'm not running a preamp on the site and the antenna is a 8 element LFA yagi.

Regards
Hayden VK7HH""

I suggest you get some measurements and look suspiciously at the filters for the band , google will help
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Re: FT-857/897 deaf on 2m?

Postby ZL2WHO » Sat Jan 05, 2019 2:40 pm

Iv had mine on a generator and I hear down to -130 ish from memory.
The only real way will to compare it with a few known good radios.. I suspect its more of a noise figure issue than being deaf.
Sinad readings would also be a good way to tell, Think I saw a sinad test on utube somewhere. As the 897 is my only radio id be keen to see where this goes.

I was contemplating a new radio until my work vehicle threw a cam belt and bent a few valves 2 days before xmas. :cry:

HNY

Mark
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Re: FT-857/897 deaf on 2m?

Postby ZL1SWW » Sat Jan 05, 2019 5:48 pm

Hi,
Well I don't have any FT 897s etc but do have some Yaesu radios. I have an FT90r in my smaller car and it was really deaf around -87 for 12 dB SINAD. After much trudging around the IF stages and checking PIN diodes etc I found that the front end tracking gain was not following the frequency. Would be easy to spot on the circuit diagram to see if there are any varicaps in the RX RF amp stages. While mine was kind of tracking it was out.
A quick test to see if the tracking is out is to run the radio down the bottom of the band in question and do spot checks on gain with the generator. Better sensitivity at the bottom end may tell you something.
At the end of the day, I found some CPU setup parameters that can change the RF tracking gain. Interesting the service manual makes no mention of tracking gain setup in the alignment menu. Some of Yaesu documentation is sadly lacking.

HTH...

Cheers,

Simon
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Re: FT-857/897 deaf on 2m?

Postby VK7HH » Fri Jan 11, 2019 10:26 pm

Thanks all for the replies on this thread.

I think next visit I’ll do an effective sensitivity test with an iso-tee. I’ll then be able to confirm how much site noise is being generated when I plug the antenna in. I’m also interested to see if my 2m amplifier is causing an issue, perhaps the noise figure on it is excessive and causing the system performance to be degraded.

I have a preamp I can put inline, and a cavity to see if that fixes any out of band signals or receiver front end overload.

Thanks all for the info.

Hayden
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Re: FT-857/897 deaf on 2m?

Postby VK4MJF » Thu Feb 07, 2019 8:19 am

Several of us had both FT857/897 the hidden menu was a help and the 2metre reception improved, remembering that I/we used 2 x 14 element yagis/with a mini kits preamplifier. IC910 for some, took their place on the bench with less improvement. Then I found the Elecraft K3, well the world is my oyster on 2 metres. As the IC910 is still on the bench because of the 70/23 cm, all with preamplifiers , but FT897 has long gone. Something I read and found, your radio is only as good as your antenna system.
John VK4MJF :J :J :J
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