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Author Topic: MFJ-1026 What am I doing wrong?  (Read 8466 times)
PA3GOS
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Posts: 43




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« Reply #15 on: March 20, 2013, 08:01:00 AM »

It sure is strange that none of the configurations you tried so far picks up the noise the way the sloper does.

I am also trying different things myself. My 25 meters long extensioncord works just fine on 40 and below. Until today it was directly connected to the 1025.
Yesterday I stopped by the local hamshop to pick up some 15 meters of Aircell 5 coax. Soldered a PL-259 on one end and tried several things to pick up the noise  loud enough on the higher bands. Like using the gutter, the tower etc.
Haven't succeeded so far.. Last thing I did was connect the center of the coax to the extensioncord. Still no luck but it works on 40 and below as before.
Only the "Phase" settings have changed of course.
Guess I have to try a shorter wire and get it up higher to pick up the noise well enough on 20 and above.

If you are going to run a sense antenna in close proximity of your main antenna you might, as I did, want to modify the sense antenna input on the unit.
An extra relay (in my case with the coil simply parallel to the existing one) pulls the sense antenna input to ground while transmitting or switched off.
This also enables you to remove the lightbulb and gain an extra 2 dB in sensitivity for the sense antenna. 

I'll try to keep you informed when I make progress.

73, Tjalling PA3GOS
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VE3TMT
Member

Posts: 499




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« Reply #16 on: March 20, 2013, 08:30:32 AM »

If you are going to run a sense antenna in close proximity of your main antenna you might, as I did, want to modify the sense antenna input on the unit.
An extra relay (in my case with the coil simply parallel to the existing one) pulls the sense antenna input to ground while transmitting or switched off.

Can you email me more information on this modification? Please email me at
mycallsign at yahoo dot ca  (ve3tmt @ yahoo .ca) no spaces

I am going to do the W8JI mods as well as I do not plan on transmitting thru the unit. I use the RX antenna loop on the FT990.

Thanks,
Max
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W1VT
Member

Posts: 898




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« Reply #17 on: March 20, 2013, 10:25:58 AM »

You will not be able to get a deep null if there is more than one noise source.

If there are two noise sources, in theory, one could use two null cancelers, one for each noise source, to eliminate both noise sources.

Zack Lau W1VT
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VE3TMT
Member

Posts: 499




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« Reply #18 on: March 20, 2013, 10:31:24 AM »

If it ever came to that I think I would just give up operating on 160 and 80. I don't really do much there now, more listening, but hard to listen with a 20 over buzz. I do have to give the 990 credit, between the notch filter and the IF shift, it does a fair job. The NB is pretty ineffective on the buzz, my old TS940's did a much better job.
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W1VT
Member

Posts: 898




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« Reply #19 on: March 20, 2013, 12:07:17 PM »

http://vk1od.net/measurement/noise/FSAmbientNoise.pdf

Here are some noise versus frequency plots that show noise levels from an ITU study plotted on a graph--together with "S Meter Readings"   to make the numbers more understandable to the average ham.

It is not reasonable to expect an "S6" noise level on 80 meters with a full size antenna--unless you actually move to a rural area! 

Zack Lau W1VT
« Last Edit: March 20, 2013, 12:37:49 PM by W1VT » Logged
PA3GOS
Member

Posts: 43




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« Reply #20 on: March 21, 2013, 01:51:43 PM »

If you are going to run a sense antenna in close proximity of your main antenna you might, as I did, want to modify the sense antenna input on the unit.
An extra relay (in my case with the coil simply parallel to the existing one) pulls the sense antenna input to ground while transmitting or switched off.

Can you email me more information on this modification? Please email me at
mycallsign at yahoo dot ca  (ve3tmt @ yahoo .ca) no spaces

I am going to do the W8JI mods as well as I do not plan on transmitting thru the unit. I use the RX antenna loop on the FT990.

Thanks,
Max

Hi Max,

Check your email. Took me a bit of time to do it but hope it is clear.
And, if you are going to use the RX antenna loop of your radio, please do connect the "control" RCA on the 1026 to the radio.
If you can't for some reason, transmit through it. This is because the extra relay has to switch to "not engaged" in order to protect the AUX input.

73, Tjalling PA3GOS
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