Hello Mike, Geri, LF
Mike, do you use a transformer between the feeder coax and the antenna?
A transformer can serve double purpose as impedance trasformer to
match the resonated antenna to 50ohm and at the same time galvanically
isolate the antenna from the coax. This requires separate primary and
secondary windings on the transformer and the coax shield must not be
earthed at the antenna end.
The above arrangement is perhaps a substitute for insulated radials
and can easily be reverted to unisolated by connecting the coax shield
to the antenna ground.
At my QTH the isolating transformer helps with interference but the
Mini-Whip still has an edge over that solution. However, when the
resonant antenna is operational it degrades the mini-whip SNR around
the resonant frequency due to coupling as the distance between the
antennas is less than 10 metres. Can't have it all at the same time
unless a "remote-detune" function is provided for the resonant antenna.
BR
Paul-Henrik, OH1LSQ
Quoting Mike Dennison <[email protected]>:
Geri,
Have you looked at your ground system? On 136kHz a network of earth
stakes works well as a receive ground. However, I have found that at
MF (including topband) I need insulated radials to reduce the
interference from household electronics, particularly my own plasma
TV. On 500kHz, the best results involve disconnecting one (but not
all) of my earth stakes, and on topband I disconnect all of the
stakes. My garden is only 20m long but I still get receive
improvements with radials.
Mike, G3XDV
==========
Yes, it's partly due to groundwave/skywave conditions but I am already
known as the crocodile (big mouth, tiny ears) over here in Northern
Germany because my signal is 599 all around while I can barely hear
people. On LF I had optimized my receiving system pretty much but on
MF I have a high noise floor, probably from household electronics. One
solution surely is to put an e-field antenna some 25m away from the
house into the garden, equally far away from all houses in the
neighborhood. Currently I am using my transmitting umbrella antenna to
receive, which always proved best on LF but probably needs some
re-thinking for MF. Additionally I got hold of a R&S EK070 on EBay
last week and I am eagerly waiting for it to arrive. At least then
nobody can complain that my receiver is lousy ;)
Lots of things to do and to explore on MF, which is a great part of
the fun. And until I am fully set up for TX and RX on 475 kHz I use
some non-amateur communication devices such as Echolink and VHF
repeaters to do my day-to-day communications ;)
Best 73
Geri, DK8KW & DI2BO
On 22.07.2012, at 19:18, Stefan Schäfer
<[email protected]> wrote:
> Geri,
>
> I bet it is only due to groundwave limitations. Normally you should
> hear Mal. So far he is the strongest signal i heared on MF. But at
> 11 UTC you can forget about MF skywave, at least in central Germany
> and in summer.
>
> Last night DF0WD and DF6NM were perfectly audible. But this is after
> 0 AM local! Later even the QSB was lower and the signals stronger.
>
> 73, Stefan/DK7FC
>
>
> Am 22.07.2012 12:24, schrieb Holger 'Geri', DK8KW - DI2BO - W1KW:
>>
>> Mal,
>>
>> Sorry, no coppy here, however, I know that my rx-equipment needs
>> improvemen. EK 070 and Mini Whip is already on order ...
>>
>> 73
>>
>> Geri, DK8KW & DI2BO
>>
>> ----- Original Message -----
>> From: mal hamilton
>> To: rsgb
>> Sent: Sunday, July 22, 2012 12:13 PM
>> Subject: LF: 502 CQ
>>
>> MF
>> Now CQ around 502 on CW
>>
>> De mal/g3kev
>>
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