Topband: Grounded half square/half loop detuning

[Guy Olinger K2AV]

Hi, Petr,

If BOTH ends of the wire are disconnected from ground and float with
nothing attached during RX, the wire is roughly three quarter wave on
160.  3/4 wave is an anti-resonant length with both ends floating.  It
should be easy to test the effect on your RX antenna.  If you still
have the problem, it may be that you have *more than one* device to
detune, or it may be a problem with the RX antenna itself.

73, Guy.

On Thu, Mar 25, 2010 at 12:09 PM, Petr Ourednik <indians at xsmail.com> wrote:
> Hi all,
>
> as I received just one reply from all of You it seems to be nightmare to
> detune
> properly this antenna isn't it?
>
> Even antenna's gurus are silent...? :)
>
> I will be glad to get any ideas as I tried a lot but my rx ant is
> useless still.
>
> 73 - Petr, OK1RP
>
>
> On Thu, 04 Mar 2010 19:01:42 +0100, "Petr Ourednik" <indians at xsmail.com>
> said:
>> Hello folks,
>>
>> I am sorry to bother all of You but according to discussion about the
>> detuning the antennas I have also question.
>> All the discussion has been made about the detuning the verticals if I
>> remember.
>>
>> I am using the big grounded half square (or maybe to say > half loop)
>> with
>> vertical sections 25m/20m and horizontal section 78m. The system is
>> grounded
>> with the wire going under surface back to the feed point where I have LC
>> network to
>> match on 160/80/40m. (switched remotely by relays)
>> On both sides I have also radial system. 4x25m on the feed point (25m
>> vertical) side
>> (I know > not so many) and 10x16m on the other side of the antenna.
>>
>> The nightmare I have with this nice antenna is that I have no space to
>> put receiving
>> antenna far away from this loop so my rotary Delta is no more then
>> 10-15m away. In fact in
>> the middle of the loop which makes the strange coupling between them and
>> the performance
>> of the receiving antenna is completely destroyed. (...I guess)
>>
>> I tried to detune the TX antenna by switching the relays to another LC
>> (80/40m when
>> I operated 160m etc.) with no effect, also I tried to disconnect the
>> coax from the TX
>> when I tried to receive on Delta with no effect.
>>
>> So simply how can I detune this big monster loop or better to say how to
>> ensure that
>> receiving antenna works well and the problem is really with coupling to
>> TX ant please?
>>
>> Any feedback or help is appreciated.
>>
>> 73 - Petr, OK1RP
>> _______________________________________________
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>