LF: Re: Top loaded vertical spiral antenne

["G3WCB" <ganymede444@btopenworld.com>]



Hello, Marcel.

 

Gary, G4WGT has done some experiments with this sort of spiral top-load antenna on 136 kHz. Take a look at his web-site, page 6. See link below.

 

http://myweb.tiscali.co.uk/wgtaylor/LF%20&%20MF%20Experiments%206.html

 

I have done a comparison with WSPR on 630m between my "standard" wire MF antenna and a short base-loaded vertical (not spiral wound) with a capacity hat. The standard antenna was a 20m long (tee) configuration with a horizontal section at 6m height and two topwires. The antenna had a vertical centre feed wire, with a loading coil in a shed under the mid point. The vertical section of the antenna is the only part that radiates. This antenna had a capacity of about 220 pF

 

The vertical antenna was a 5m fibreglass fishing rod with a capacity hat made from six 60cm long radials (wire coathangers!), with a loading coil inside the garage about 2m up from the bottom. I didn't measure the capacity of this antenna but I would expect it to be about 80 -100 pF.

 

I found that running the same RF power (15W) to the vertical produced WSPR reports that were about 10 dB weaker than the "standard" MF "tee" antenna. This performance could be improved by simply running 10dB more power to the vertical antenna! I would imagine that a spiral wound antenna would have a perfomance that would be one or two dB better than a base-loaded vertical.

 

I didn't do any comparison of the two antennas on receive, as I used a separate 60cm square tuned loop for reception on 630m

 

There's a picture of the vertical antenna and loading coil on my QRZ.com page.

 

http://www.qrz.com/db/g3wcb

 

73, Dave G3WCB IO80DI

 

 

----- Original Message -----

From: Marcel Bos

To: rsgb_lf_group@blacksheep.org

Sent: Monday, June 01, 2015 10:11 AM

Subject: LF: Top loaded vertical spiral antenne

Members,

My backyard is in the city 8 x 8 m.  My intention is to do some experiments on 472 khz.

Ready: RX converter 0-500 khz 10 mhz osc. and K3, RX ant. pa0rdt whip and receiving loop

TX: GW3UEP 100 watt, RF meter, and variometer 30 uh -600 uh

Now i'm looking for a antenne. Found a article from Finnbar EI0CF and Alan G3NYK about the spiral toploaded vertical.

Has any body tryed this antenne, is the original article availble.

What is the distance between the wire's  of the spiral?

Also talking about a double spiral?

So who is gone help me out  ore has some better suggetions for a antenne in my backyard

http://www.xeropage.co.uk/g3nyk/spiraltop.htm#aerials

tnx in advanced

Marcel

PA9M