Anybody on this list have a Rhombic for 160M?
W1AW used to use one for bulletins and code practice on 160M but I think it
came down years ago (1989?)
I seem to recall pics in CQ of a big California desert DX'er who had what was
essentially a radial array of rhombics for maybe 160M or 80M.
Tim N3QE
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Grant Saviers
Sent: Friday, July 26, 2013 11:03 AM
To: ZR
Cc: Gary@ka1j.com; topband@contesting.com
Subject: Re: Topband: Topband Inv-L Joy
Posted on towertalk yesterday was the link to the free download of the
1952 text Radio Antenna Engineering
http://www.lulu.com/us/en/shop/edmund-laport/radio-antenna-engineering/ebook/product-17560294.html
Some fascinating stuff since much of the focus is high power
broadcasting LF/HF and point to point reliable RF links with high gain
HF wire antennas. (many pictures of amazing arrays). A quick peruse
found in a later chapter how to build high power non-inductive
terminations for rhombics etc. Make an open wire feeder of the needed Z
from iron or stainless wire and as long as the db's you wish to absorb
and with wire heavy enough to handle the current. Clever stuff,
invented when HF was a primary long distance communications technology.
The formulas are there for resistivity and ferromagnetic losses.
Of course some of the content is now pretty irrelevant since we have
cheap great coax, ferrite, and NEC software and a billion times the
worlds 1952 total computing power on every desktop.
Grant KZ1W
On 7/25/2013 8:17 AM, ZR wrote:
> On a side note WD-1A conductors are a copper/cadmium alloy; whatever
> that means in RF resistance. Fine for a Beverage but what is the loss?
>
> Carl
> KM1H
>
> ----- Original Message ----- From: "Gary Smith" <Gary@ka1j.com>
> To: <topband@contesting.com>
> Sent: Thursday, July 25, 2013 1:22 AM
> Subject: Re: Topband: Topband Inv-L Joy
>
>
>> Had a more difficult time getting the antenna up there this time. The
>> first spud snapped away from the fishing line & in the dense thicket
>> I was unable to find where it landed. Had to make another & the
>> mosquitos were so thick they posted a LUAU sign on my forehead.
>>
>> Till I get something better I retrieved my WD-1A military field phone
>> wire that was left out in the marsh as my old beverage wire. and
>> after a comedy of errors I finally got the antenna up.
>>
>> I was earlier getting a SWR of 1.1 on 160 before and now am getting
>> 1.1 on 1.74365 MHZ
>>
>> 1.74365mhz
>> R=51 X= 6,7,8
>> swr 1.1
>>
>> At the desired frequency to match the antenna I've aimed for 1.8MHZ
>> here's the information I was able to get at my desired frequency:
>> 1.8025 mhZ
>> Coax loss 6.3db
>> C=4193 XC=21
>> L=1.970 X1=21
>> r=41 x=21 swr 1.6
>>
>> So this is what the antenna is giving me at this moment. I need to
>> get back down and add the broken wire to the radial bed and I should
>> also trim some length to bring my values to 1.1 at 1.025MHz.
>>
>> Given the info above from the MFJ 259B any idea how much I might
>> nibble off and more, is there anything in this info that tells me I
>> should look to do anything differently?
>>
>> Hopefully the coax loss will be mitigated by a friend bringing me
>> 350' of hardline. Can't wait!
>>
>> Thanks,
>>
>> Gary
>> KA1J
>> _________________
>> Topband Reflector
>>
>>
>> -----
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>
> _________________
> Topband Reflector
>
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