Tuesday, April 5, 2011

Made an active antenna to compare

To compare with the K9AY loop i made a small active antenna  
to the concept of PA0RDT  http://yu1lm.qrpradio.com/pa0rdt%20whip.pdf
I used a strip of double sided copper  clad  epoxy print 200x30 mm.
The amplifier is a FET  U310  and  2N3053 emitter follower.


This small capacitive antenna  did fit in a cycle bidon (bought on the Alp de Heuz once..) 
Interesting this antenna  is only picking up the Electrical-field. 
It is also a good RFI sniffler.


I used a relative big pickup plane of about 3x20cm  at the risk of IMD but i wanted to compare this E-field antenna on the 137kHz and 500kHz bands.








It works but the DCF39 TX at 138.9 kHz is about 30B stronger on the K9AY Loop. I have to check that out the difference should not be that big.
That was at the low position (top picture).
I moved it on top of the house about 8m a.g.  
Now DCF39 138.9 is s9+30   the difference is about 20dB in disadvantage against the loop. The high position gave 10dB more signal. I have heard OK2BVG good on 502kHz.
The higher bands give S9 noise  to much signal for the IC706  the preamp has to be switched off. Heard DL/KL1A good on 40m with it... 
It is better than nothing... but i compare it with a real good loop in the open field.
It has the advantage that it is very small and wide-band.
A good travel companion.









  

1 comment:

Bert, PA1B said...

Hallo Jaap,
Dat ziet er goed uit op de foto.
de mini-whip is een interessante antenne.
Ik vraag mij af of 200 x 30 mm niet véél te groot is. Ik meen mij te herinneren, dat het kopervlak ook maar iets te groot wordt, dat er dan intermodulatie optreedt.
De versterker is immers héél breed.
Ook EPO in je bidon brengt dan geen uitkomst meer. ;-)
Succes, Bert PA1B

Translate