Which Coax

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Which Coax

Postby andy5600 » Tue Mar 11, 2014 9:16 am

Hello all,

Need to join up a balun (Long wire)to my receiver but due to practical reasons this will need to be done with a 10m length of coax with a pl-259n at each end. Have had a quick look and choices seem to be RG-58, RG213 or Westflex 103.
I know signal losses are a factor but do these make a big difference for this length of coax.
Not too sure which to go for, Anyone have any advice in this area?
Thanks,
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Re: Which Coax

Postby Mark5R » Tue Mar 11, 2014 10:34 am

Personally I use RG213 as it has a lot less loss than the regular RG58. RG58 is OK and not much loss at HF and low VHF but when you get to high VHF and UHF at 10 metres length there will be a few db loss which will be noticible. The way I see it is that if I am spending money on good quality receivers and antennas then I am not going to skimp on the cable.
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Re: Which Coax

Postby m0lsx » Tue Mar 11, 2014 1:28 pm

If you are using a long wire, then it will be for HF & thus RG-58 will be fine..
At HF there is minimal power loss over 10 meters of RG-58, however, having you antenna in that configuration, you have the ideal opportunity to improve things cheaply & simply..Use a earth stake connected by a short wire to the 9:1, this will reduce noise levels at the RX.
The best set up for a longwire is to have a remote tuner at the feedpoint, this will make the biggest difference to performance, as there is significant loss in the coax due to the poor impedance at the antennas feed point.
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Re: Which Coax

Postby m0lsx » Tue Mar 11, 2014 1:40 pm

Putting figures into a coax loss calculator...

10 meters of cheap very cheap & nasty RG-58 at 30 MHZ & the losses get higher with frequency, so this is a worse case scenario for HF..
With a SWR of 1:1..The losses are..
Total loss....1.556 dB, that is about 30%
At 7mhz the loss is about 15%

With good quality RG-213 & a 5:1 SWR...

Total loss 0.689 dB, or about 15%..
At 7Mhz the loss is about 8%

The above are based upon the cheapest most nasty RG-58 (Tandy) & Wireman RG-213,, which performs much better than Beldon..If you used unbranded average RG-231, the gains in 213 or 58 would be much much less.
Last edited by m0lsx on Fri Feb 06, 2015 3:05 pm, edited 1 time in total.
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Re: Which Coax

Postby andy5600 » Tue Mar 11, 2014 5:27 pm

Hi,
Thanks for that info, helped me decide.

Have went for rg-213 for the moment, will do some experimentation in finding the best site for the long wire.
Maybe upgrade a bit more in future

Thanks,
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Re: Which Coax

Postby m0lsx » Tue Mar 11, 2014 7:40 pm

During the last Scout Jamboree On The Air I threw my approximately 20 meters of wire up across the car park, just out of reach of hands, it was certainly no more than 10 feet at it's highest point & over the weekend we worked over 30 different location prefixes if you include both the Irish calls, Wales, Scotland, Isle of Man & the different prefixes for Italy etc etc..
My standard special event station antenna is a 9:1 strung between any convenient point & it is a good & simple antenna..
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Re: Which Coax

Postby andy5600 » Mon Mar 17, 2014 10:12 pm

That sounds like a good and easy set up, is that onto a handheld?
my own wire (20m)is not much more than 10 feet up, lack of trees or anywhere good to fix to
seems to work ok.
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Re: Which Coax

Postby m0lsx » Mon Mar 17, 2014 11:46 pm

Not a handheld no, JOTA is Jamboree On The Air & is where amateurs take our kit in & let the Scouts talk to amateurs & other Scouts from around the world. The radio was my Icom IC-728. It is a simple to use radio with no menu's just buttons for each function, so if any other amateurs are present, they don't need a manual in one hand to use it.
We worked all over on that wire, my best QSO ever, on the antenna is an 80 meter QSO with a station at the Spanish F1 race. On that occasion my antenna was slightly off vertical up the side of a medieval church tower. The wire is just one out & about, portable antennas & only used a few weekends each year, as if I can I use one of my other antennas which are centre or off centre fed.

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