Re: [VHFcontesting] Pre-amp questions

[jeff millar <wa1hco@adelphia.net>]

I made some different choices on my 90 Ft Rohn 25 tower

Most important, bought a house on a hill overlooking a vally in my 
primary direction (SSW)

Tied off the top guy 10 ft below the top of the tower to leave room for 
H frames with antennas below the top
Placed the tower against the house, short run for feedlines straight 
into the shack.
Feed lines come in through 6 inch PVC pipe through hole drilled in 
wall.  Enter at ceiling of basement shack
House mount bracket at first point where guys would go.

Water  got into rotor cable at top and ran down though cable and poured 
out over shack table, had to put a drip hole in the sheath.

Plan on stacking 432, 1296 antennas vertically using H frame

M2 5 elements on 50, decided against 7 el due to wind load
Cushcraft 13B2 on 144, upgrading to M2 this summerSurplus 7/8  or 1/2 
inch heliax for all feedlines
Homemade FO22 on 432

Surplus 7/8  or 1/2 inch heliax for all feedlines
Separate feedlines for each antenna, no preamps (yet)
Preamps create lots of failure modes and introduce connector and jumper loss
Preamps fail a lot due to lightingSurplus 7/8  or 1/2 inch heliax for 
all feedlines
Big used  coax seemed like a better choice than complex preamps

With good feedline, preamps on 50 , 144, and 222 MHz just hurt the 
dynamic range
Preamp on 432 would probably help a bit, but the station preforms just 
as well as the 144 under most propagation

Running the rig barefoot clearly puts me at a disadvantage.  Can't work 
WSJT, can't work the weak big gun stations
Will add an 700-1500 Watt amplifier before adding preamps
Antennas may not take take 1500W...need to power divide and stack them

hope this helps...

jeff, wa1hco

Michael A. Urich wrote:

> In approximately a year or so, we are selling and moving out into the
> country where I can grow steel and aluminum.  I am not going to have the
> problem of being burdened with too much money, so like many radio
> projects, putting a station on the air is going to have to be done in
> stages.  The trees where we are looking at land are in range of 70-80'
> tall so the first order of business is a good tall tower. I'm considering
> going up with a 100' Rohn 45G tower.
>
> The rig in use will be my Yaesu FT-736r equipped with 50/144/222/430
> bands.  And at the moment my antenna choices are:
> 50 MHz = C3i C7-50
> 144MHz = C3i FO 15-144
> 222 MHz = C3i FO16-222
> 432 MHz = C3i FO22-432
>
> My vision is to run a single LMR-600 feedline to the top of the tower and
> then switch it to masthead pre-amps with LMR-400 runs to the antennas.  I
> intend to use a NEC weatherproof box at the top of the tower for the
> pre-amps and switch. The LRM-600 will terminate in the shack into another
> switch with LMR240 going to the four modules of my FT-736.  Somewhere in
> the future I will be adding RF amps for each band as the $$$ permit.
>
> My question is, have any of you, or do you know of anyone who has tackled
> a similar project?  I am also looking for suggestions on mast head antenna
> switching and recommendations for pre-amps.  I'm also wanting ideas for
> lightening protection area as well.
>
> Mike Urich, KA5CVH
> www.ka5cvh.com
>
> Mike Urich, KA5CVH
> www.ka5cvh.com
>
> Mike Urich, KA5CVH
> www.ka5cvh.com
>
> _______________________________________________
> VHFcontesting mailing list
> VHFcontesting@contesting.com
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>
>  

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