432 MHz - pictures of OK1TEH's equipment

432 MHz - pictures of OK1TEH's equipment

23el DK7ZB yagi - 5,7m boom, gain 17dBd, it's home made by OK2BJL - http://www.mydarc.de/dk7zb/70cm-longyagi/23-ele.htm

Assembling of the elements for a 23el DK7ZB at OK2BJL

The Radiator-Box

Measured (tnx OK1BAF) Data at DK7ZB web: http://www.qsl.net/dk7zb

The old LNA (1990) with MGF 1502 (placed in shack, 0,45 dB NF), TNX OK1VPZ

Because of terrible QRM from CDMA "Ufon" provider we had to use cavity filter (att. about -2,5dB)..

I compared my RX with Jiri, OK2POI. He has 4x12el yagi with gain 19,5dBd, cable with the same attenuation like me (-1dB) and LNA with the Noise figure of 0,45dB. However Jiri has real RX measured with EME stations 6dB better. While the calculated difference is 19,5 - 17 = 2,5 then 6 - 2,5 = 3,5dB. As Jiri, OK2POI has his QTH in quiet mountains, my RX is killed by the local noise + QRM, digital TV an 3m radio tower just 200m far from antennas + UFON cdma provider for -3,5dB. PS: I use cavity filter only during elevation below 15degrees.

January 2010 - New band pass filter

On 15th January 2010 I got new 70cm cavity band pass filter. Measurements provides after retuning:

Old cavity B.P.F. from NMT network: transit att. of -2,0dB, return att. -18dB, selectivity ± 600 kHz / 10dB

New cavity B.P.F. (on left): transit-att. of -1,3dB, return att. -20dB, selectivity ± 100kHz/± 1dB; ±10MHz /±30dB, middle QRG 432.100 MHz

New B.P.F. provides 0,7dB better RX and allowed me QSO with W7MEM. Except big advantage of transit attenuation new cavity filter is much more stable with temperature - when we put if from 20°C warm room to -10°C balcony and then get it back (after few hours), the frequency changed just some few kHz off - the result: Compared to the old cavity B.P.F. I don't need to tune it manually.

432 MHz 1HP tube PA with GS31B (finished by OK1VPZ in 1990)

OK1VPZ 70 cm Power amplifier with GI 14 b (or GS31b, GS1, GI39 ) tube - more at http://www.ok2kkw.com/ok1vpzpa.htm