HIGH SWR!

[ehsanspicedigital]

Hello hello

4 BW BROADCAST 6db Antennas, being run through a harness coming down to the TX with LDF 550 to an elenos ETG 400/1K

Randomly the transmitter went from out usual 6w of SWR to 75w @ 1kw, knowing the ratings of these elenos PSU’s i’ve got it running at ~ 850w where SWR is 56w.

This happened suddenly, and it’s really effecting transmission coverage. My first instinct was to re-do the DIN connector on both ends at the Harness and at the TX, to see what happens?

What do you lads advise, there’s also a connector inbetween the line coming from the TX, so
i need to check this also, but i thought id get a few ideas from you lot before i start re-terminating these cables.

The pics of the antennas are from about 1 year ago during inspection and maintenance!

[ehsanspicedigital]

One of the antennas was down for inspection already! that’s why you can only see 3 in this photo

[King Croccy]

Well I would be inclined to first connect a dummy load to the cable whilst it's in situ. I know this is easier said than done but it would eliminate the transmission line from the equation. Very often water can get in the terminations particularly as you mentioned you had an inline connector. Drop the power to the tx to whatever the dummy load is rated to and see if you are getting good swr.

In the past I've been called out to sites, the guys had an inline connector in the feedline. Snow had settled on the coupler connector and as it was running warm, it melted and water got in the connector. All had to be re-terminated and heatshrink tubing was used to protect the joint from moisture.

Not sure what aerials you have (they look like high power broadband ones). If any of them have threaded ends where the elements join on, it's worth checking them for corrosion inside. A lot of them dipoles you buy on Ebay suffer from this issue. Water gets in, causes corrosion and the swr goes of lol. I always put heatshrink on them now when they have been tuned on the block

[ehsanspicedigital]

So, What i’ve basically done right now is re-terminated the inline connector as it was a bit loose and minor signs of arcing/sparking. When I turned the TX back on to try it the SWR has gone down from 56 to 48w. I am in the process of taking down all of the antennas and connecting them directly to the TX to see wether it could be an antenna problem as i don’t have a dummy load on hand with me as this setup is in Pakistan and im here now, without all my resting equipment.

The TX is out of the equation as my spare 500w Elenos showing the same value.

Testing all the antennas and will get back to you.

[ehsanspicedigital]

All of the antennas are showing 0w of SWR @ 500w, i don’t want to take it any higher on one antenna. It’s now either the harness or the wire itself. They’re re-terminating the connector at the top of the tower and i’m re terminating the one at the TX now.

[ehsanspicedigital]

So, i have a feeling after cutting and re-terminating the connections there might be a mismatch in the phasing. if i understand correctly the RF output from each antenna should be in the correct phase to avoid phase cancellation between each dipole? This is the final thing i can think of before we pull down the LDF550 going up to the tower and run some impedance and resistance tests and just visually inspect the wire itself. What do you guys think?

[Frequent Lee]

Those figures are Reflected Power NOT the swr level. That's basically saying that for the 881 watts of power out of the transmitter, 56 watts is coming back down the cable and wasted. You need a proper dummy load and proper swr meter to get the true representation and numbers.

[EFR]

If I did math right, 881W in and 56W back means SWR is about 1.7

[ehsanspicedigital]

well. we found the cause of it now. the wire was rubbing against the metal work and it’s done this. Replacement wire should be here today!

[ehsanspicedigital]

i don’t want to cut and re-terminate and add another connector here, there’s already one and i feel it’s better to just replace the wire as a whole to reduce the losses on them connectors

[ehsanspicedigital]

YES! It’s sorted now 975w FWD and 12w RP! Is this now an acceptable figure?

[fmuser877]

nice Easy fix

[EFR]

Its now about 1.25, much better.

[radium98]

Nice fixing . I would like to know how i can easly making from rg6 or rg11 a phasing harnes for2 dipoles matched on 88.5Mhz for just a 100W. I am a bit old but new for this technik.
Thanks.

[ehsanspicedigital]

I’ve got a word document somewhere that is a calculation you have to input a few values and it gives u the right length the phasing harness should be I’ll have a look for it and post it if i find it

[radium98]

Thanks for you in advance

[teckniqs]

YES! It’s sorted now 975w FWD and 12w RP! Is this now an acceptable figure?

Well that should do nicely into those 4 aerials giving you approx 4kW.

....I gather this is NOT being used for a pirate radio.

[teckniqs]

I am a bit old but new for this technik.

I thought you were talking to me then for a brief moment haha.

[ehsanspicedigital]

[/quote]

Well that should do nicely into those 4 aerials giving you approx 4kW.

....I gather this is NOT being used for a pirate radio.
[/quote]

running 4kw on a pirate would be diabolical

it’s a fully licensed FM station. we’re covering a 350mile radius

[ehsanspicedigital]

Thanks for you in advance

Here is the Link. I think it is this one. Was written in my diary!

https://dev.dw1zws.com/downloads/phasin ... lator.xlsx?