IC-7000 Receiver Problem

[VK2AAH]

Hi all,

Can anyone help? My IC-7000 had a weird receive problem that seemed to only effect 80m. High constant noise across the band- about S7, S9 with preamp. Stronger signals just audible above noise. Did a factory reset this morning but noise was still an issue. Other bands were fine...

Any ideas? My first thought was that I've stuffed up the filter settings but nothing seemed to improve the problem.

Cheers

Richard
VK2AAH

[VK2GOM]

Have you tried this test on a dummy load or an antenna?

73 - Rob VK2GOM / GW0MOH

[VK2AAH]

Hi Rob,

Only on an antenna- if I disconnect the antenna the noise is gone. The best way I can describe it is that incoming signals seem to be clamped to about the same level as the incoming noise, which makes it very tough going.

Cheers

Richard
VK2AAH

[VK7TL]

Hi Richard,

I'm very new to forums etc - forgive any Newbie mistakes. I had a similar problem on 20m - turned out to be a heatpump - they seem to put out a strange "wideband" signal that "dampens" receiver sensitivity - hard to locate, but it had a similar effect on my RX signals. Then a choice between good RX or getting slowly colder - Hi Hi ! A few well placed ferrites on the heatpump control lines seemed to help.

Good luck, 73's Tom VK7TL

[VK2LK]

Hi Richard,

I hate to ask an obvious question, but is the problem the same in Sydney as it was down at Cootamundra?

Cheers,
Matt

[VK2AAH]

Hi Matt,

First time I've seen it happen. I used this same radio in the last 80m Trans Tasman from my Sydney QTH without a problem. I'm going to make enquiries about the heat pump theory because on this farm there is a very large solar farm & the farmer may also have installed a heat pump system in the house. It is very possible & something I had not considered. But why only 80m? Using the 80m OCF 40m was about S1, 17m was about S2 noise floor and both perfectly normal receive.

Cheers

Richard
VK2AAH

[VK3AIF]

My first uneducated guess would be something local generating the noise be it heat pump, plasma tv, crook insulator on a pole or whatever? If you can take a receiver for a drive up the road you might just be able to narrow down the location of the source.

Good luck

[VK4TI]

Hi Rob,

Only on an antenna- if I disconnect the antenna the noise is gone. The best way I can describe it is that incoming signals seem to be clamped to about the same level as the incoming noise, which makes it very tough going.

Cheers

Richard
VK2AAH

Sounds like you have a common noise source , does the radio have a dc operation ?

normally one would close the house power off and run the rx from dc then having confirmed the noise is house generated switch the house back on bit by bit until you find it .
It could be a number of things like a wall wart , a/c tv etc , is the noise constant across the band or is it the banded rise and fall we usually get from pc style gear ??

I had a bad 40M problem disappearing after rain which proved to be a ground lead on a power pole a block away being loose and swinging .

[VK3DXE]

First thing I'd do is try a different radio in the same location or same radio at another location to rule out local noise issues. Logical really.

[VK2AAH]

First thing I'd do is try a different radio in the same location or same radio at another location to rule out local noise issues. Logical really.

Hi Alan,

And that is precisely what we did... we switched to a FT-817 and while the noise was still S7-8, the "clamping" effect I described didn't effect the Yaesu. That was why our thought was that the Icom had to have an issue. Could that be the DSP interacting with the type of noise (the heatpump theory)? I don't know but I'm making more enquiries today- whatever it was the farmer wasn't home at the time so the nearest plasma was miles away and the noise impacted only on 80m- weird.

Cheers

Richard
VK2AAH

[VK4GHZ]

Just DF the source of the noise?
Even without a directional loop etc, a short length of wire will do, and take a drive in the X direction, then in the Y direction.

If you remember the ANC-4 noise cancellers, they did a pretty good job of minimising this sort of interference.
I used mine for minimising powerline noise at the last QTH.

Found this demo


I believe the ANC-4 is still available under the TimeWave brand these days.

[VK2AAH]

The noise is not the issue Adam but how the radio dealt with it. DF'ing it wouldn't achieve anything because when you are operating portable from someone's farm you just need to be grateful for having the privilege to be a guest there... but I do want to know why a radio with the level of digital sophistication of the IC7000 could not deal with it as well as a more basic radio like the FT-817. And I also want to learn if it was my misuse of the filtering that may have contributed. If I had started the contest with a radio with the receive performance of the FT-817 but 100Watts instead of 5Watts our score would have been much higher than the 900ish we finished with. We will be back next year so we want to be prepared for this issue- we definitely got the antenna right!

Cheers


Richard
VK2AAH

[VK2AAH]

Owen VK1OD has sent me his theory on this based on testing of the IC7000 he has done. This data is published on his website. To me I think Owen's theory that it is caused by fast rise time noise causing the AGC to dampen the receiver rings true. It suggests to me that maybe in this particular location the IC7000 is not the best choice of radio and I could be better off with something like a TS2000 (or even my mates FT817 but with a 100W amp behind it).

Thanks to Owen & everyone else who have offered advice. I'm now looking at doing some more field tests before we go back in July for the 160m contest.

Cheers,

Richard
VK2AAH

[VK3DXE]

First thing I'd do is try a different radio in the same location or same radio at another location to rule out local noise issues. Logical really.

Hi Alan,

And that is precisely what we did... we switched to a FT-817 and while the noise was still S7-8, the "clamping" effect I described didn't effect the Yaesu. That was why our thought was that the Icom had to have an issue. Could that be the DSP interacting with the type of noise (the heatpump theory)? I don't know but I'm making more enquiries today- whatever it was the farmer wasn't home at the time so the nearest plasma was miles away and the noise impacted only on 80m- weird.

Cheers

Richard
VK2AAH

OK, a little more info brings a lot more light

With the IC-7000, you can press and hold the NR button to change the DSP Noise Reduction level. Similarly with the NB and Manual Notch Filters.

I've found that running the NB at 100% seems to be best, EXCEPT on some strong SSB signals which it chops to pieces. The Manual Notch Filters are great with some noise sources when you set them to WIDE and adjust their frequencies to make a rudimentary bandpass filter.

The NR setting can be a little fickle, depending on the noise source, but try adjusting it to 0%, then slowly bring it up while listening to a signal and note where it starts to get "woolly". I usually find (in my very noisy location, on 2m) that a setting of 3 - 4 works well. Anything more and readability drops off quite rapidly.

Hope this helps.

FWIW, you were quite strong on 80m during the contest and myself and a number of others were calling you, but you obviously weren't hearing.

[VK2AAH]

Thanks Alan, it is a pain not having the antenna up at home any more... at least then I could be testing these suggestions. I'll try & see if there is anyone around Sydney I can test the radio with...

Thanks for letting me know that & it was frustrating- always hate having a bigger mouth than ears. The QTH is great & I'll definitely go back again for 80m next year. Same antenna but we will come armed and ready to deal with the noise. And a 2nd radio op... my good mate decided he enjoyed the data entry role but my vocal chords could have done with a rest.

Cheers


Richard
VK2AAH