PP selling a lot of stuff from BBC Cardiff, Lots of tables and chairs etc. but in there is: Lot 2371 3x Xicom TWTA travelling wave tube amplifiers (spares or repair) No picture, no type No.! I think t

I would try a piece of bar, say 8mm thick with clearance hole, use the tap to line it up then clamp it and you have solved the "keeping it straight" part, probably better than by eye. I have some "Tre

But ..but.. you are my hero, I thought you knew everything there was to know about all such matters!

I have a 15W PA 3.7-4.2 GHz which had a (very neat) welded lid. I eventually decided it had to come off which proved to be quicker and easier that I expected on the mill. In fact it had a conventional

I noted that for some years Radiall connectors are available with "BBR" plating, a form of bronze. According to their publicity (of course) it is better than anything else considering cost, corrosion,

I have a few 4.1-9.5 connectors, (and a 6dB attenuator) if anybody has a use for them. They were in the 1970's Plisch TV amplifiers, a few of which made it into amateur service.

HP141 SA: If anybody takes this to use, all you need to do is replace the neon with an appropriate zener diode. I did years ago and it has never taken out the fuse since.

Arved , 1) If ripple is result of a mismatch on the cable it will be regular in frequency, based on the frequency at which the cable is half wavelength long. 2) Mismatch on the cable is a result of th

Yes, Mark, when I started in 1975, the (ridiculously heavy, 55kg, according to radiomuseum.org) SWOB 2 was the standard kit we took to site to test antennas. Tracing paper and a Chinagraph pencil reco

Filters (like the ones you make?) would be perfectly symmetrical for 50 ohms in/out. Significantly different coupling arrangements at each end would make it into a transformer; 50 in 100 out or what e

Hi Andy, Having looked at your original link, I suspect that the design is not a three pole filter, but is a two pole filter. The middle screw is not a resonator, but will affect the coupling between

Yes, as Andy beat me to it, set it up looking at the return loss. I would say 1) You don't need to concern yourself with anything greater than 30 dB return loss - it is meaningless in terms of any pra

Hi Chris, The article you remember is there somewhere, I looked at it earlier this year, but cannot find it now. I think it was an Italian author, but I could be wrong. The original circuit is simple

Like this one, Mark. 88-108 MHz. Ken YKI Not yagis but some big band II transmit antenna use spearhead X dipoles which sit in front of a reflector. These have elements about 6 inches in diameter. Powe

Hi Robin, Thanks for the kits. Your system worked perfectly. Only took an hour or so to assemble the two boards. Ken.

I think you will find that the Andrew cable with helical corrugations was called FHJ4-50 and stopped being made about 40 years ago, when they went on to LDF4-50 with "annular" corrugations, same as RF

Hi, Paul In analogue TV broadcasting days the radiated delayed image was the critical factor in determining the antenna impedance specification. So exactly as you say, the reflection from the antenna

As a picture is worth a thousand words, they say, (and without implying that RF propagation is exactly the same as optical) the two attached photos illustrate this sort of effect. Taken from near sea

No Pictures? Some Radiall relays I have looked in have double coils in series in the actuator, so if nominal 24V operation can easily be modified for 12V.

Hi Richard, I built a dish, 2.4m, in sections, for portable use, but when I stopped going portable, used it at home.(Even though not designed for permanent outdoor installation, and it was eventually