[50mhz] 6 meter newbe

[Bill W5WVO]

w2drz wrote:

> Did the "S" meter go way down and the buzzing go away.
>
> If so, need to find what computer and other digital devices that are
> causing the interference on the rig. Turn off all you can find until
> the noise is eliminated. Then turn on one at a time to find those
> causing the noise. The fix is beyond this note and up to you on the
> fix.

Boy, I was going to write that, but Tom beat me to it. You need to get your
man-made noise level down to where it doesn't register on the S-meter, or
you'll have a hard time of it on 6M except during the strongest openings. I
went through this whole drill some years ago. Here are the worst cuplrits I
found:

Desktop Computers -- especially their switching power supplies, which are
often poorly filtered. This is particularly true of the higher-wattage ones.
They have to fit all the components into the same size box irrespective of
the power requirements; the high-power supplies (400-500W) do this by
forgoing niceties like noise filtering components. Basically, you need to
equip the power cord with a common-mode choke (big ferrite donut), or
several in series -- enough to absorb the energy before it can be radiated.
There are lots of other things in computers that can make noise, too, but
I've found 95% of the serious noise usually comes from the power supplies.
Read the ARRL's RFI Handbook for lots more info.

802.11b/g wireless gateways/clients. These transmit as Part 15 (unlicensed)
devices; their signals are sometimes rich in harmonic content. There's not
much you can do with the bad offenders except get rid of 'em and try another
brand that is maybe designed and built a little better. (Or forgo the
wireless and just use Ethernet.) Out of three wireless gateways I have
tried, one generated lots of harmonic trash on 6M, the other two none.

TV RECEIVERS generate radiated noise as harmonics of their approximately 15
kHz oscillators. This is typically radiated into the air by the power cord,
which must be equipped with a common-mode choke (same as computers) as close
to the receiver as possible.

Low-voltage Halogen light switching-type power transformers and light dimmer
switches. Again, some of these cause noise and some don't, varying with the
design and the amount of filtering built in (if any).

Cross-modulation products generated in your receiver by the mixing of
multiple strong out-of-band signals (intermod). The typical cuplrits on 6M
are low-VHF TV and FM radio broadcast transmitters in your immediate
vicinity. You can find out if this is a problem by inserting a 10 or 20 dB
attenuator inline with your rig. (Don't transmit!) If the noise just gets
weaker but doesn't change qualitatively, then you probably don't have this
problem. If the noises go away entirely or their characteristics change
significantly, then you probably do.) If intermod is a problem, it can be
fixed by installing a good low-pass or band-pass filter between your rig and
the antenna. DCI (www.dci.ca) makes a variety of models that are extremely
good (albeit expensive). You can also homebrew your own filters. (They must
be beefy enough to withstand your transmit power.)

This is just a quicky summary of my own experiences. There are TONS of other
man-made things that can cause noise on 6M. Get the RFI Handbook from ARRL.
Worth its weight in gold.

Bill W5WVO

>
> A S7 noise back ground is very strong,
>  this will prevent you from hearing stations that you normaly can
> work.
>
>
> If this is the problem and you find the noise fix, you will be good to
> have fun.
>
> tom W2DRZ
> FireBrick wrote:
>>
>> I managed to get my used icom706mkIIg set up.
>> I have the 6 meter elements on my Sommer yagi, (nested to 40' right
>> now due to winds).
>>
>> I see the cluster spots but I've only really heard one station,
>> about 10 miles away.
>>
>> I do hear noise come up to s7, but nothing intelligible as a signal
>> listening 50.125 and .135 USB but so far just buzzes and noise.
>> Both the rig and an outboard swr bridge indicate a pretty good match.
>> Also have a VL1000 inline but so far just ran barefoot.
>>
>> I'm still reading this manual and trying to figure out this rig.
>> A little confused that when I 'set' the filters, that I got the cw
>> filter with cw and the narrow ssb filter with ssb.
>>
>> 40 + years of hamming, and first time on 6 meters.
>>
>> -----------------------------------------------------
>> Blessed is the end-user who expects nothing, for ye shall not be
>> disappointed.
>> -----------------------------------------------------
>>
>> Bill H. in Chicagoland
>> webcams at http://24.14.49.4:8080
>> weather at http://hhweather.webhop.org
>>
>> Moderator: Ray Brown, KB0STN
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