Hey, I have a new problem. Its an "AC buzz" type sound coming through. It starts about every 2 minutes and lasts almost exactly 23 seconds. It starts gradually (comes up over about 2 or 3 seconds) but stops suddenly.

I have a G5RV and hear this on several radios across HF (My Icom 7000 Noise Blanker clears it up).

As a test, while it was buzzing I turned off each circuit breaker one by one, to no avail.

Anyone had this isssue or know how I can hunt it down? The houses are close together here. I'm thinking a power line (transformer?) issue or some equipment in a house but no idea what, or how to track it down...

Dont forget this one...

http://www.youtube.com/watch?v=Yy-4TX9zrVw

thanks charles, how to change the 7000 to 150hz - 3khz?  I looked at the menus, only could find transmit bandwidth not receive...

hi all,

I just acquired a Drake SW2 (and  Degen 1103 for when I'm on the road) for SW listening.  This is a great opportunity to compare a few radios. My main station rig is the IC7000, a great radio, but terrible audio. I bought a bearcat external speaker which is muffled, not better.

First thing I noticed about the Drake SW2 (besides the incredible sync det) is the audio quality is so much clearer, and smoother. Not harsh. I know the little internal speaker is puny and not great, but since I already took a stab at one external speaker, thought of putting it out here as to if there is any significantly better speaker that works well with the 7000?  Looking for something on the smaller side as space is very limited.

as to these 2 new additional radios, please dont tell my wife LOL

Rick I still need to test the limits of my BCB reception anyway now that I have learned the tuner was in the way (and replaced it with a similar tuner that has a bypass switch).  I also need to add a loop as well. In order to work with a loop, it will probably have to be in here with me in the living room, although I could put a loop of about 5' diameter in the attic above and have a large knob in the ceiling to rotate it, or better yet coming down the wall with a wooden lever, the top (in attic) would have a bellcrank with a push pull rod about 10' to the attic center where the loop can be mounted in a bearing. That would get me close to 180 degrees of rotation which would cover all directions.

There are wires around my attic, I wonder if that will affect the loop's performance or properties?

The source of the problem is that a signal below the 20uv sensitivity wont be processed by the radio. I can get more signals above 20uv by improving the antenna, but there will still be weak signals that COULD be heard without the attenuation. So THAT problem is inside the radio. Of COURSE I would not find a way to switch it off on my own I am not a digital radio tech. But I am hopoing to find someone here who can do just that.

Put it this way, I want to move the <1.8 attenuation to OUTSIDE the radio where *I* can control it, not be forced to listen only to stronger stations because it cant presently be switched off.

Hopefully I didnt stumble upon a IC7000 purity religious cult here  lol it is just a radio and I am a hobbyist looking to get a choice in MW attenuation, and there is nothing wrong with wanting to do the attenuation optionally rather than mandatory.

I think we're talking past each other here. I know that it will be fun and productive tpo work with loop antenna options. But the sensitivity still could be better. Of course I can filter OUT the strong BCB RF before it gets to the radio. I still want to find the way to mod the attentuator out of my radio, even though i do hear the concerns - but your concerns should be nulled out by the tuner which BLOCKS BCB totally, or any high pass filter of my choice in the unlikely event my tuner makes a water landing...   

Hi Martin I totally read you on your opinion of the way forward. Actually, the attenuator is my tuner since MW does not make it through. I would like the option to explore different antennas such as various loop options, vertical wire and others and would like full sensitive on the radio. I dont want to be forced to have a limited signal when I can do that outside the radio such as automatically occurs with my tuner, and I could also use a high pass.

Hopefully you and others understand my position. If my radio can be 10x more sensitive internally, I would like that choice for myself. I would not try to dictate what others should do in configuring their shack as these are very near and dear choices we all love to make.

If my 7000 can be made 10x more sensitive internally below 1.8 I would really like to see if any of the very knowledgeable Elmers around here would know just where to make that mod. If anyone here knows how to bypass this artificial limitation inside my 7000 would you please share any info you have, as always thank you!

Allison there is a coil of coax near the junction block at the start of the twinlead.  But I do now get MW now that I bought a tuner with a bypass switch.  This thread has answered a lot of questions and I am learning a lot.

I would like to mod the radio if possible to defeat the MW attenuator as a next step. There is really no good reason not to since MW cant make it through my tuner when it is switched in.

Anybody care to look at the service doc above and point out any clue as to the nature and location of te attenuator and especially if there is a relay associated that can be jumped or disconnected?

UPDATE there is no menu option to turn off the MW attenuation on my IC-7000 so I'll be looking for someone who can work on this radio as I'm sure with the 2uv to 13uv sensitivity drop at 1.8MHZ, its there...

I found the service manual here:
http://www.repeater-builder.com/icom/pdfs/icom-ic-7000-sm.pdf

I dont think this language applies to our issue but it says this about below 1.8

The signals below 1.8 MHz are passed through the low-pass
filter (L103, L104, C106, C110, C111) and then applied to
the preamplifier circuit.
The other band signals (1.8–60 MHz) are passed through
the high-pass filter (L105, L109, L110, L116, L117, C108,
C109, C114–C116) to suppress strong signals below
1.8 MHz and then applied to the low-pass and high-pass filter
circuits.

OK I went looking for a schematic (still looking) but the manual lists AM sensitivity up to 1.8MHZ is 13microvolt, and above 1.8MHZ it drops to 2microvolts. So I am certain you are right. I am no electronic tech so I'll look for that menu option. If there is none, I'll certainly need some kind of help getting the attentuator disengaged if possible...

Got my MFJ-945E today. First try it seems like a good little tuner, and it has the bypoass switch so I get moderate MW performance. The old tuner (with no bypass) was filtering out the MW band.  But I can get 740 Toronto in my car, but not on the Icom with the G5RV (can get many other stations though). Someone mentioned an attenuator that switches in, I'd like to find that but also I will get an old AM car radio and try in in place of the IC-7000 just to rule in or out the antenna, location, etc.

There is an SO-239 on the bottom of the 10M stick.  My coax goes from this straight down in the window to my switch then tuner.

I am reading up now on Baluns which as Charles said, SWR can be fine at the radio and still have major RF coming off the coax feedline all the way down to the rig which I am now sure is my issue.

I am wondering if a 1:1 current balun up at the antenna feedpoint will just stop RF coming back down, or if in fact I would also gain performance in radiation efficiency (more RF going out the vertical). Either way this looks like what I need.

I had thought that a balun was just to match a balanced to unbalanced not for this other function.

Here is some info I'm looking over:
http://www.g0ksc.co.uk/creatingabalun.html

Charles, the chimney the mast is on is right behind me. About a 25' coax comes right off the bottom of the vertical to my switch. (I disconnect it and toss out the window when it storms).

There is no ground plane on the antenna although they do sell one and there is no room for a ground radial system. Thsi house is 3' from the property line and the chimney is halfway down that side.

I like the current balun idea the descriptions mention stopping RF coming back down, perfect. And have a question, this product says it runs the feedline through ferrite beads:

http://www.hamradio.com/detail.cfm?pid=H0-002260
The W2DU Maxi-Baluns owe their extremely high power capability to the fact that they contain no ferrite cores to saturate. Even at high SWR levels, the W2DU Baluns won't generate harmonic radiation. The internal feed line passes through ferrite beads which prevent RF current from flowing on the coax shield.

So I do have a box of high grade ferrite snap togethers, would those do me any good or is there some engineering within the commercial product above?

Hey all, I meant to ask this for a week now.  When on 10m and the antron vertical mounted on a chimney mast with the base approx 20' high, and I tune up on low power to a 1:1 SWR, then go to full 100w power, my computer monitor gets heavy interference and even shuts down.  

When I modulate itr comes out the nearby surround subwoofer speaker. I notice when tuning up that as I dial the match in, the interference gets much worse. Shouldnt it be the other way?

This tells me the RF is not all going out to the antenna where it should be.  The antenna has RG58 down to the alpha delta switch, then a short patch to the Icom.

Not sure where to begin because the radio and tuner show a good match so shouldnt the RF be staying outside? Something doesnt seem right though.

I do have an MFJ 259B antenna analyzer but not sure what to look for...  (and I do realize *maybe* there is really no problem, I can contact my fellow hams on 10m - not really quite what it should be but its ball park with the gang, sluightly subpar and that could be my locale.)