Help me pick which antenna best suits my new QTH

[VE7 Kilohertz]

Previous post about scope pattern desribes my current new setup and my new QTH. My lot is 100M x 800M, long line running North/South. No trees on my property but the neighbours have a few big firs on either side of my lot. Basically my house is centered in the lot, and I have trees about 60-70' high on either side in the east/west direction. So my only choice is to use those, which will give me an antenna with wire running east/west at about 30' in the center (droop) and 60' at the ends. Distance between the trees is about 115M which is about 370'.

I would like to use my homebrewed #12 with johnson spreader ladder line, and my heavy duty balanced antenna tuner with major pair of roller inductors (~22 uH) and big ass vacuum variable (26-1000pF) with 30' of coax wound on ABS pipe balun.

So with 370' at my disposal, with the shack basically centered right underneath the antenna path and single suports on either side of the lot, what would give me best results, least RFI for mostly operating on 160M and 75M?  I have up right now, 120' on either side, dipole, which works okay on 160M, loads fine etc, but have some huge RFI issues on 75M, and can't get positive peaks out of the Bauer.  would going to .64 wavelength for 160M get me anywhere? I think that would be a current fed antenna on both 160 and 75 if I read the handbooks correctly.

Look forward to your thoughts.

Thanks!!

Paul

[WA1GFZ]

Paul,
How about a Vee Beam if you have enough feed line to get to the side of the lot.
I would like to see a picture of your tuner to see how high it goes on the vortex fugly meter. Sounds great. This would move your feed point away from the house and distribute the current to two conductors. Also it would be up higher since the feed line is supported by the trees. A Vee 370 feet on a leg should do the job! Also could make it a 2 wire Vee and spread the ends to lower the Q.

[AF9J]

A v- beam is cool if you have the space.  Remember, a true v-beam is at least 1 wavelength long, and will give you gain compared to a dipole.  If you don't have the space for one, you can do like I did in the 90s on 6m - make a 1/2 wave long pseudo v-beam.  I had the V in the horizontal plain, and it worked pretty good.  It also had the added benefit, of having some directionality (I made mine out of copper conduit, and used it portable, rotating it with the armstrong method).

73,
Ellen - AF9J

[WA1GFZ]

make the angle at the center as wide as possible so the length is as long as possible. It will work. Heck on 75 that will be close to 2 wavelengths on a side. The good thing is the field is distributed over a big area and hopefully away from the rig.

[Steve - WB3HUZ]

Modeling your 370 foot system shows feedpoint impedances something like 115 + J 1158 Ohms at 1.9 MHz and 97.56 - J 105.6 Ohms at 3.8 MHz. I don't know the length or type of feedline you intend to use. You can plug the above numbers and the specific feedline data into the URL below and learn what sort of impedance your tuner will see. You can also see if you are at at or near a current or voltage node (more likely to cause RFI problems).


http://fermi.la.asu.edu/w9cf/tran/index.html

So my only choice is to use those, which will give me an antenna with wire running east/west at about 30' in the center (droop) and 60' at the ends. Distance between the trees is about 115M which is about 370'.

I would like to use my homebrewed #12 with johnson spreader ladder line, and my heavy duty balanced antenna tuner with major pair of roller inductors (~22 uH) and big ass vacuum variable (26-1000pF) with 30' of coax wound on ABS pipe balun.

So with 370' at my disposal, with the shack basically centered right underneath the antenna path and single suports on either side of the lot, what would give me best results, least RFI for mostly operating on 160M and 75M?  I have up right now, 120' on either side, dipole, which works okay on 160M, loads fine etc, but have some huge RFI issues on 75M, and can't get positive peaks out of the Bauer.  would going to .64 wavelength for 160M get me anywhere? I think that would be a current fed antenna on both 160 and 75 if I read the handbooks correctly.

Look forward to your thoughts.

Thanks!!

Paul

[k1qar]

Paul

Seems like you already have decent current feed, close to 3/4 wave on 160 (115m/160m) and 1 1/2 wave on 75. 

First mod: possibly tune out the RFI by adding a tuned counterpoise underneath, should reduce ground currents and add performance.

or second, do trial and error additions  or subtractions to the antenna itself.   Find which end of 75 is the worst FRI, and tune away from that.  e.g. if the low end (3.5 Mc) is worse, then the antenna ought to be decent somewhere above 4MC, so add wire to bring that sweet spot lower.  If the 4 Mc band end is worse, then the cleanest freq is somewhere below 3.5, and wire needs to come off.   

A third possibility is to add a captive pole support to elevate the center by getting feeder weight off, getting the high current part up higher and changing the tuning by reducing induced ground currents (similar to cutting wire)

[ab3al]

sounds like a job for a plasma dipole..

[KA7WOC]

Paul,
I was out in the shack last night working on the Barney rig and listened to the 1845 QSO.  CCA sounded fine while the band held, unfortunately it did not last for very long.  I don't notice much difference in signal strengths between the former and the current QTHs.  Keep it bright.
Talk to you soon.
woc

[VE7 Kilohertz]

Paul,
I was out in the shack last night working on the Barney rig and listened to the 1845 QSO.  CCA sounded fine while the band held, unfortunately it did not last for very long.  I don't notice much difference in signal strengths between the former and the current QTHs.  Keep it bright.
Talk to you soon.
woc

Hi Bob,

Thanks for thr report. Glad my signal is still getting into yoru part of the world.

Yesterday I extended the antenna to make it an extended double Zepp on 75M but am now having trouble tuning it.

Starting a new thread for this.

Chat soon.

Paul