Tom, I have used the JPS ANC-4 and it works wonders on local power line
noise. I went from a S-9 to S-3 noise level with no loss of distant siginals
strength by using one. My buddy who has used them both says the MFJ is even
better but I do not have first hand knowledge with that model. Got local
noise? Get one and say good by to iWilliam Lee
-----Original Message-----
From: Tom Scott <tscott@eni.net>
To: 'Ten-Tec Users Reflector' <tentec@contesting.com>
To: <tentec@contesting.com>
Date: Tuesday, April 27, 1999 11:59 PM
Subject: [TenTec] Power Line QRN?
>
>A warning that this is a bit long-winded... please bear with me... I'm
>curious to get some feedback...
>
>Now that I have finally gotten my Omni V operating better and greatly
>improved my antenna deployment, I finally can see what has given the Omni V
>its reputation for being a "great set of ears". My best antenna is a
>G5RV-length dipole fed with ladder line from a Johnson Matchbox. This
>antenna is sloped between thirty feet and seventy five feet off the ground.
>I'm getting wonderful sensitivity now, but the downside is that I'm getting
>quite a bit of power line QRN at my QTH.
>
>I knew this problem was likely before I set up this station given that my
>lot is on a hilltop just adjacent to a utility company right of way for
high
>tension towers. Among the advice I got beforehand was that given the rain
>here (Oregon), one of the chief sources of trouble - dirty power line
>insulators - might be somewhat diminished. Truthfully, the noise is not
>intolerable, I do get DX sources, but with my RF gain at maximum and all
>extra filters off, I am seeing a noise floor between S5 and S6. With the
>wonderful crystal ladder filters in this rig (I now have the 217, 287, and
>285 added, still looking for a 282), I can do wonders with CW stations, but
>it is harder to deal with SSB (yes I know, some of you will say "what's SSB
>(hi hi)", but I do enjoy listening to phone as well). I can hear a lot of
>voice down in the noise that is just not copyable.
>
>I am investigating several approaches to treating the noise problem and
>would welcome any and all comments and suggestions:
>
>One thought that immediately came to mind was to experiment with a DSP
>solution. I just happen to have a Motorola 56002 EVM board that I've
>discovered has been the object of much amateur radio experimentation in DSP
>filtering and data modem development. So I've been reading and downloading
>things from a very good web site that Motorola directed me to for
>ready-to-use software and application notes for this board. I have not
>gotten very far with that yet, and don't mind getting some education in
>DSP's in the process; but I'm no expert in the field, and I'm sure this is
>going to take some time to learn.
>
>I've also heard from two sources that another treatment may be effective.
>That is a technique for receiving the QRN with a device that is essentially
>an out of band receiver which nonetheless receives essentially the same
>power line QRN which is then inverted and with careful phase adjustment,
>used to cancel the QRN as a common mode rejection. I have found what
appears
>to be one such device from JPS Communications, their ANC-4 for around $190.
>(MFJ has something that looks very similar (MFJ1025 or MFJ1026), but I
think
>it actually uses a different technique, that of nulling signals from a
given
>direction. That wouldn't be very useful in my case since the power lines
are
>along a broad line to the east of me where much of my listening would be
>directed.) I understand from an old Motorola commercial communications
>systems engineer that they once used that technique, but one flaw in the
>theory it had was that in a crowded metropolitan area you could have
trouble
>locating the necessary alternate frequency band that was devoid of traffic.
>Any signal other than the QRN in the alternate receiver would not cancel
>properly with the QRN signal in the primary band and would therefore become
>an inverted spurious QRM in the primary band.
>
>I have several questions:
>1. What kind of noise floor do others with a comparable rig experience?
>2. Does anyone have experience with the Motorola 56002 EVM or independently
>developed DSP algorithms?
>3. Does anyone have experience with the JPS ANC-4 device (or the MFJ
1025/6)
>or something similar, and what do you think of its effectiveness for this
>problem? Does the JPS technique seem like a worthwhile approach to try?
>4. Does anyone have experience with any other DSP device or technique for
>treating this level of power line QRN?
>5. Any other suggestions / comments I haven't mentioned?
>
>If you got this far I have to thank you very much for your time and
>patience. I really value the collected wisdom I've found from this group.
>
>Thanks!
>
>-Tom
>_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
>Tom Scott -- KD7DMH
>14623 SW Peak Court, Tigard Oregon 97224
>503-603-1931 - Day 503-684-6620 - Eve
>503-504-1583 - Cell 503-604-8651 - Pager
>_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
>
>
>
>--
>FAQ on WWW: http://www.contesting.com/tentecfaq.htm
>Submissions: tentec@contesting.com
>Administrative requests: tentec-REQUEST@contesting.com
>Problems: owner-tentec@contesting.com
>Search: http://www.contesting.com/km9p/search.htm
>
--
FAQ on WWW: http://www.contesting.com/tentecfaq.htm
Submissions: tentec@contesting.com
Administrative requests: tentec-REQUEST@contesting.com
Problems: owner-tentec@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|