I thought a Hertz was a dipole...
"R.Measures" <r@somis.org> wrote:
On Dec 26, 2004, at 12:40 AM, Alek Petkovic wrote:
> Have you thought of a section of open wire line in the feedline at the
> feed point which puts the equivalent amount of wire into the loop to
> resonate it on 75m?
>
> eg: a 75m loop for 3.9MHz is around 258' and for 7.2 MHz it would be
> 140'. That is a difference of 118'. If you were to use a 59' section
> of open wire, it would put 118' of extra wire into the loop.
>
The wire in a balanced feedline does Not add to the wire in the antenna
-- i. e., antennas and feedlines are not like series resistors. .
The best antenna I have used for limited space on 80m - 160m is the
(end-fed against gnd) Hertz. A 100' by 60' lot will accommodate a
fairly efficient Hertz antenna. The tradeoff is that a
remote-controlled L-network is required at ground level at the driven
end of the wire.
> If it is not possible to do it that way, you could perhaps put one or
> more loading stubs, say at the support points, still using open wire,
> to make the antenna up to the total required length.
>
> I have not tried this but it could be a cheap solution and well worth
> some experimentation.
>
> Good luck,
> Alek. VK6APK
>
> ps:
> I hope to be making a nuisance of myself on 75m over the next week
> from my beach house using my 2 x 3-500z and Carolina Windom 80. Watch
> out for me. I'm heading down there tomorrow.
>
>
>
>
> At 12:53 PM 26/12/2004, JimMoci@aol.com wrote:
>> Happy holidays to all on the amps reflector. I have an off topic
>> question
>> about a loop antenna so if it is not appropriate please remove it or
>> respond to
>> me directly via email. I am asking here because there are so many
>> experienced
>> and knowledgeable people on this reflector and the info I receive
>> will be very
>> useful.
>>
>> My situation: I currently have a full sized 40 meter delta loop @ 30
>> ft and
>> it is horizontal to the ground. I use it on 40 thru 10 with good
>> results. The
>> antenna exhibits a good SWR on 40 and an SWR less than 2.5:1 on 20
>> thru 10
>> meters so the internal auto antenna tuner in my Icom solid state amp
>> can handle
>> the mismatch. What I would like to do is use it on 75 meters but dont
>> have the
>> room for a full sized 75mtr loop. The loop is to small for 75 and has
>> an very
>> high SWR, to much for the internal tuner to deal with. So far I have
>> tried
>> splitting it in the middle, essentially a full sized 75 meter dipole
>> folded back
>> on itself. It works ok, but not a stellar performer. It also lost the
>> advantage
>> of being a quiet receiving antenna, a characteristic loops are known
>> for.
>>
>> I have a couple ideas that I want to try but figured I would ask
>> before I go
>> climbing tress out in the cold. The first idea was to add another
>> full turn to
>> the loop, separated by a few inches. Essentially it would be a 2 turn
>> loop,
>> totalling about 260 feet, but only taking up the space of a 40 meter
>> loop. The
>> other idea was to add a large inductor in the middle of the loop. I
>> have a
>> large, silver plated, flat wound inductor from a broadcast
>> transmitter that would
>> do nicely. I also have a vacuum relay that I could use to short it
>> out for 40
>> thru 10 mtrs.
>>
>> My main question is will the two turn loop work? If so will it be
>> better than
>> the inductor?
>>
>> I realize that I could use a large roller inductor tuner in the shack
>> but
>> that defeats the purpose of my lazy hams push button station. My
>> solid state
>> kilowatt is silent and automatic and it is my goal to keep the
>> station totally
>> push button.
>>
>> Thanks for any and all advice- It will save me many trips up the tree
>> and
>> there is snow in the forecast. Why didnt I do this in the summer?!?!?!
>>
>> 73,
>> Jim W3ATV
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>
> http://www.qrz.com/vk6apk
> http://profiles.yahoo.com/vk6apk
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
---------------------------------
Do you Yahoo!?
Yahoo! Mail - Easier than ever with enhanced search. Learn more.
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|