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Re: [RFI] Mast-mount TV Pre-Amp -- Avoiding RFI & Overload?

To: doc@kd4e.com
Subject: Re: [RFI] Mast-mount TV Pre-Amp -- Avoiding RFI & Overload?
From: "Roger (K8RI)" <k8ri@rogerhalstead.com>
Date: Fri, 05 Jun 2009 00:13:22 -0400
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>

kd4e wrote:
>> When you say "out int he woods", are the stations close (strong 
>> signals), far, (weak signals) or a mix?
>> Are they all (more or less) in one direction?
>> What distance ranges and headings (or bearings) are we looking at?
> We are north of Tampa and all of the signals come generally from
> that direction.
> Arm-strong rotation of the beam requires only a tiny movement to
> bring one group of stations in strong and lose several others or to
> have the majority of them and a few lost but several at the compromise
> position are erratic.
>> Some have filters, some have a filter for the FM and 2 meter band and 
>> some don't.  HOWEVER unless you have some really strong TV stations, 
>> or the 50, 144, and 440 antennas are going to be very close and of 
>> the same polarization I wouldn't be overly concerned to the point of 
>> losing sleep. 
> I operate 6, 2, and 440.  The closest of those antennas is about 30 
> feet off the
> back-side corner of the TV beam.
> I currently run less than 100W on 6M and less than that on 2 & 440.
As I mentioned in the other post, I run a KW up through 144 into the 
array and up to 160 watts on 144 simplex on the Diamond, side mounted 
vertical. Normal power is 2.5 to 5W for the repeaters
> The 6M antennas are a Delta loop and a horizontally polarized beam -
> the beam is not yet up but will probably be fixed west-northwest - so
> back-to-back to the TV beam (and 30 feet away).
> I also sometimes use a dipole via a tuner that is further away and my 
> 6BTV
> HF vertical which is ground mounted about 20 feet away from the push-up
> pole that supports the TV beam.
Here's one view of the antenna set up.  The TV antennas are not shown in 
this photo as they are not mounted, but they are currently above the 
thrust bearing plate below my feet.  Also not shown in this photo, but 
in the one below is the side mounted 144/440 vertical along with the 
sloping dipoles on 75 and 40 with the half sloper on 160 to the south.

While this one gives an overall view showing both TV antennas. The one 
pointed to the left (NW@330deg) stands out, while the one pointed 
straight South is difficult to see, but it's almost at the same level as 
the one pointed NW.

>> I would get a bit better remote preamp though
> Someone recommended a Winegard and I am looking at those - bonus
> that is it USA-made!
and they have a good reputation.
>>> Since using a mast-mount pre-amp will eliminate the need for a rotator
>> What makes you think it will eliminate the need for a rotator?  I'm 
>> not saying it wont, but if the stations are at a reasonable distance 
>> then you may not even need a preamp.  If the stations are mostly in 
>> one direction and the antenna is a relatively simple one like a 
>> corner reflector of dual bow tie with a screen reflector then it's 
>> likely you can get away without a rotator.
> The TV beam is a multi-element on VHF and on UHF, it is intended
> for fringe use.  I don't know the brand as I received it used.
> We have a lot of UHF TV stations here in the Tampa area.
 From SE to SW (Detroit to Grand Rapids) I pick up about 20 on digital 
although no few have the same programming which makes them redundant. To 
the NW I only pick up 2 which are out around 80 plus miles.  (Cadillac 
and Traverse City)  I'm reliably receiving stations out to 90 miles or more.
>> I would go with a better amp, but I think many get overly concerned 
>> about possible problems.If it's a simple system, put it up, try it 
>> and modify it if necessary.
>> 73 Roger (K8RI)
> That was helpful info, thanks!

Roger (K8RI)
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