Any rust on that tower/antenna or on the galvanized rope that is used to crank
it up?
-Mike, KE6MRE
> On Oct 19, 2015, at 23:09, Roger (K8RI) on TT <K8RI-on-TowerTalk@tm.net>
> wrote:
>
> There are a lot of possible spots where the mixing can happen.
>
> This brings up the question: Mixing with what? Nearby AM stations, ham
> bands, and why every 10 KHz? What is the primary station, or stations and
> their frequencies?
>
> "Any section" making poor contact with those above or below, making contact
> with coax braid, tension causing poor contact in connectors.
>
> It's pretty certain it's related to cranking the tower up, but is it due to
> poor contact in that position, or that it picks up more signal?
>
> I assume the mixing is gone during the raising and lowering process. If not,
> does it just get weaker as the tower is lowered?
> I'd be surprised that it's not strong near the full extension while moving.
>
> Places to start:: If the mixing is only present at full extension, check for
> tension on the coax at the antennas, rotator loops, and at the cable stand
> offs. Check the cable jackets, particularly where they pass through the
> stand offs. Check cable jackets where they can move against each other.
>
> Use a VNA to check all coax at full and partial extension. Don't ignore
> rotator cables and connectors either
> If you don't have one, beg, borrow, or purchase one. With the tower fully
> extended on a windy day, watch the traces for changes. Have you tried a
> spectrum analyzer? Even the ones in the newer rigs can be helpful, but you
> need to look between the bands as well.
>
> Check the places on the tower sections where the skids/pads contact adjacent
> sections for excessive wear and or missing galvanizing,
>
> When the local repeater was here, I could block a 50W mobile a mile or two
> distant simply by rubbing a 10" screwdriver against any of the galvanized guy
> wires which were broken up with insulators. I had a TB3 tribander just below
> the repeater antenna @ 90 feet. Legal limit on 10, 15, or 20 did not bother
> the repeater.
>
> 73
>
> Roger (K8RI)
>
>
>
>> On 10/19/2015 10:03 PM, Rich Hallman - N7TR wrote:
>> Has anyone had any problems with intermittent mixing from a close broadcast
>> station with a Crank-Up tower? I think I may have an issue with one of my
>> towers. Cranked up I hear mixing all over 80 meters (Every 10
>> KC).....Cranked down its gone. I already eliminated the antennas. Mixing
>> gets very intermittent in wind as the tower moves around.
>>
>> Thoughts about grounding the top section to the bottom when fully extended?
>> Was thinking of grounding the coax at the top and bottom of the tower?
>>
>> Thanks....
>>
>>
>> Rich N7TR
>> ex KI3V, N3AMK, WB3JOV
>> www.n7tr.com<http://www.n7tr.com>
>> http://www.qrz.com/db/N7TR
>> Telnet: dxc.n7tr.com N7TR DXCluster
>>
>>
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>>
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>
>
> --
>
> 73
>
> Roger (K8RI)
>
>
> ---
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