[NLRS] 10 ghz dish feed

[Dr. Gerald N. Johnson]

I used the 3/4" water pipe dimensions from N2LIV published in a ARRL
microwave projects book. I put the short as a flat plate in place of the
original PC board and as I recall the dimensions were that the probe was
0.468" from the short and the probe was .220" long, something like .090"
+/- diameter.

> K0AWU has a write up on his web site. I did something independently
> of that. I took out the polarization septum and the PC board. I made
> an aluminum plate to close the PC board end that I sanded flat. I
> drilled the tapered wave guide to 3/4" diameter. Then I mounted a SMA
> connector with probe from an article in proceedings about using 3/4"
> water pipe for 10 GHz waveguide. I think the probe was .220" long
> about .100 diameter spaced .080 from the connector insulator that I
> made from a couple bits of brass tubing, and something like .467 from
> the shorted end of the guide. I've not checked match, but feeding a
> Direct TV dish that came with the LNB, it did 32 dBi at MUD last
> fall. And with 100 mw out and a 15 dB NF receiver I worked about 130
> contacts with NLRS from Buck Hill last September. I can't say that
> tuning might be of benefit.
>
> I found one version of the water pipe waveguide article in the ARRL
> book UHF/Microwave Projects book volume 2. There are several articles
> in this book about rectangular horn feeds for DSS dishes, that also
> work well.

K0AWU and N0EDV do it differently with the probe further from the short
and then they introduce a tuning screw through the short, maybe with a
slug that nearly fills the waveguide. K0AWU has a web page about it. But
the only links I can find are on the departed geocities.

I suspect tuning screws in mine would improve the match, but I'm not
convinced the improved match would compensate for the loss in the tuning
screws. It measured 32 dBi (Direct TV dish and feed) at MUD last fall.

73, Jerry, K0CQ

On 8/1/2010 10:12 AM, Marciniak, Ed wrote:
>
>
> Can someone point me toward a link to a drawing/template or other
> instructions? What I’m looking for in particular would be one with
> probe dimensions, backshort position, etc. with the WG bored out to
> ¾” rather than the stock 0.693"