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Re: LF: MF mobile ?

To: [email protected]
Subject: Re: LF: MF mobile ?
From: Tobias DG3LV <[email protected]>
Date: Thu, 28 May 2015 01:35:10 +0200
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Hi Stefan !

but most likely there is a LOT of
QRM when driving...
It depends on the type of car. While testing /mobile on 160m I did not
hear QRM from my 23 year old Diesel. At the Autobahn, far away from
cities there is almost no QRM from outside. I had a lot of fun, and a
lot of QSOs. (Antenna Pro-Am 160m, PA 300W). The HF-QRM-situation on 475
should not be worse.
A capacity head (with skirt) as large as possible and a top loading coil
should be possible to build (4m x 1.6m, 1.5mH). It certainly will look
somewhat similar to the foto from F6GEX. For legal reasons your car +
antenna may not be higher than 4m, this leaves 2.6m for the vertical
part at the 1.4m rooftop of the car. The mechanics would be a challenge.
73 de dg3lv Tobias

Am 28.05.2015 um 00:10 schrieb DK7FC:
Hmm, i find someone should do a real mobile (mobile-mobile, with a
velocity > 0) experiment. A 1.5 m long CB antenna with a special
preparated feed point should work. And i think that the wire works
better with a fixed C in parallel, even if this reduces the efficiency.
But it stabilises the SWR or better said, the voltage on the wire.
Corona? Where is the problem with corona? :-)
Markus, could you calculate the ERP when 10 kV rms is applied to a 1.5m
high antenna on a car roof? I bet you have all the formulas in your mind :-)

Maybe the antenna has 10 pF. I remember i have a 470pF/16kV capacitor at
home. So if C = 470 pF and f = 475 kHz, L = 239 uH With 470 pF parallel
to the antenna, a moving wire (= changing C) does not make a significant
effect i think.
10 kV at 239 uH at 10 kV is 14A. If P = 200 W, the losses must be 1 Ohm !
With a good RF litz wire, this is possible :-)

What would be the ERP and possible distance?

It would be interesting to try that in WSPR / QRSS-60 :-) I would also
drive to someone for making a CW QSO but most likely there is a LOT of
QRM when driving...

More ideas?

73, Stefan

Am 27.05.2015 15:58, schrieb John Langridge:

>Perhaps a 2 meters whip is a bit too short ?

The smallest antenna that I have experimented with was a base loaded
vertical that was almost 3 meters long and I observed reasonable
success with about 100w TPO.  The radiator was a 2 cm diameter
aluminum antenna tube so charge was distributed pretty well and no
corona was observed.  There was no additional top loading in the test.
  I was using a fair radial system at the time but perhaps its time to
try this same arrangement in a fixed mobile setting as you have done

I look forward to hearing about your further experimentation.  I hope
you will conduct this test again in the winter.



*From:* Guyé André <[email protected]>
*To:* RSGB LF Group <[email protected]>
*Sent:* Wednesday, May 27, 2015 7:05 AM
*Subject:* LF: Fw: De F6CNI : WSPR Test using mobile on MF to night.

Hello Markus.
I am sad about my experiment, only one station copied my very loud
signal last night : F5WK at 72 km. Perhaps a 2 meters whip is a bit
too short ?
For a next experiment, F6GEX just give me an other mobile antenna
shape idea. Intesresting indeed ! Be sure, I’ll give to you also the
results of the doppler effect. HI.
Best 73 de Andy F6CNI.

*From:* Markus Vester <mailto:[email protected]>
*Sent:* Tuesday, May 26, 2015 7:06 PM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: LF: De F6CNI : WSPR Test using mobile on MF to night.
Great Andy, this is a wonderful experiment!
If you could persuade yourself to drive on a highway while
transmitting, would we be able to measure your speed using Doppler
effect? Probably not using WSPR, but surely with QRSS-60...
73, Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: Guyé André <[email protected]>
An: RSGB LF Group <[email protected]>
Verschickt: Di, 26 Mai 2015 1:47 pm
Betreff: LF: De F6CNI : WSPR Test using mobile on MF to night.

Hi to all.
I’ll be testing this evening WSPR 2 and at times WSPR 15 on MF using a
short mobile antenna. My call be F6CNI/M.
Of course, I don’t drive my car, it is resting in my garden…

  * TX power 2 Watts ;
  * Antenna is a 2 meters long whip ;
  * Total Antenna Z = 85 -16610 j. Using base L tuner to 50 Ohms ;
  * Antenna base current = 145 mA, base voltage = 2400 Volts RMS ;
  * Average expected soil up to the Fraunhofer zone : 0.003 S/m and 13
    for dielectric ;
  * Effeciency about – 43 dB. Maxi lobe is -40,5 dBi at 22° site ;
  * Apparent radiated power is about 150 micro Watt, and the E.I.R.P.
    is about 270 micro Watt.

Reports be appreciated.
Begining the experiment this evening at 2000 TU to next morning, but I
think the best period is around 2300 to 0200 TU.
Best 73.
Andy - F6CNI – JN19QB

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