POTY with 90 degree close connector?

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Basil
Posts: 160
Joined: Tue Sep 10, 2013 7:28 pm

POTY with 90 degree close connector?

Post by Basil » Sun May 22, 2022 12:44 pm

I want to use som LDF4-50 as the POTY feedline. To do so i need a connector coming out the side, rather than the back of the POTY, will this be a problem please?
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g0mjw
Posts: 1897
Joined: Sat Sep 20, 2014 9:15 am

Re: POTY with 90 degree close connector?

Post by g0mjw » Sun May 22, 2022 6:03 pm

Try it. Too late now if it is not, but you would have been better off using a short tail of semi-rigid. The problem with LDF4-50 is it's not very flexible and it will tend to want to go where it wants to so may be difficult to tame. A short bit of semi-rigid gives some flexibility. You only need a connector on the far end of the semi-rigid, you can solder it to the feed directly.

90 degree conectors can be a problem at microwave frequencies, but as long as it is a high quality one, e.g. Schuner, it should be OK.

Mike

Basil
Posts: 160
Joined: Tue Sep 10, 2013 7:28 pm

Re: POTY with 90 degree close connector?

Post by Basil » Sun May 22, 2022 8:25 pm

Thanks again Mike. I could use a straight on the dish end of the LDF4-50, rather than that 90, but would have to sweep the coax in front of the dish more.

I have some genuine Andrew straights, that 90 cable end fitting is a copy, but it LOOKS ok, for what that's worth. I'll just try it in due course, as you suggest. I think I can unsolder that 90 N type off the POTY if I had to, and clean the brass back up.

You mean solder the prepped end of some semi ridgid direct to the POTY itself??

g0mjw
Posts: 1897
Joined: Sat Sep 20, 2014 9:15 am

Re: POTY with 90 degree close connector?

Post by g0mjw » Mon May 23, 2022 7:15 am

Basil wrote:
Sun May 22, 2022 8:25 pm
You mean solder the prepped end of some semi ridgid direct to the POTY itself??
Yes, that's right. solder the outer to the reflector, the inner to the patch and try to avoid any stress/flexing on the solder joint.

Why use an extra connector when you don't have to? Connectors always introduce miss-match, this becomes increasingly important with higher frequencies and higher power. Minimising the number of connectors/adaptors inline is usually a good idea. It also saves the cost of buying high quality connectors and adapters.

The UT141 size semi-rigid should be able to handle the power, just don't have it too long. UT141 loses about 0.2 dB per foot and will handle 200W CW at 2.4 GHz. A six inch length should be more than enough and the 0.1 dB loss will be negligible in practice.

Don't even think about using the very cheap connectors available online in this application, they are not suitable for high power at 2.4 GHz.

Mike

Basil
Posts: 160
Joined: Tue Sep 10, 2013 7:28 pm

Re: POTY with 90 degree close connector?

Post by Basil » Mon May 23, 2022 8:02 am

Thanks, I looked up the specs for that 90 degree adapter I soldered to the antenna and it's rated to 11GHz, so I feel confident in giving it a shot as is. However your warning re right angle connectors made me also check the spec of some LDF4-50 90's and the one in my photo is rated to only 2GHz, so I will use a straight. Next time I'll try semi ridgid directly soldered, but currently I can't see any adapters to go from UT141 size cable to LDF4-50.

I am beginning to see an analogy between microwaves and race engines (which I do understand...). An engine only revving to 6750 RPM is relatively easy to make reliable with low internal losses. Less so one turning 10750 or more RPM!

Appreciate your advice and time.

radiogareth
Posts: 933
Joined: Wed Jan 06, 2016 9:46 am

Re: POTY with 90 degree close connector?

Post by radiogareth » Mon May 23, 2022 9:47 am

Here is what I did, using some nice ex-military sma to N-type, cut off the sma part to use in a pipe-cap filter, leaving this bit. I used a 50W Weller iron with a big 500C chisel bit, it took a while, but got there in the end including the bracing strip.
POTY feed.jpg
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Gareth

Basil
Posts: 160
Joined: Tue Sep 10, 2013 7:28 pm

Re: POTY with 90 degree close connector?

Post by Basil » Mon May 23, 2022 11:11 am

Very neat and sanitary Gareth, I like that, and wish I'd done it similarly now, but I think I should at least try what I have first. Thanks for sharing that.

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