Many thanks to SWLing Post contributor, John Minor, who writes:
I am going to set up a rig to start DXing, and getting my technical license. My plan is to buy a Kenwood TS-590 SG transceiver and a discone antenna.
My home’s previous owner had satellite TV, and my question to you is, can I use the existing cabling for my antenna?
There is a connector in my living room, and the cable runs to the connector/splitter box for the dish. Could I run a cable from the end of the existing cable at the splitter box, to the antenna?
I’ve attached some pictures to show you what the existing cables look like.
Picture 6 has a circle drawn on it to show where I’d like to mount the antenna.
I remember back when I was 9 or 10, laying under the covers at night slowing turning my AM transistor radio dial and seeing what I could pick up. It was a thrill to hear stations from Chicago, Cincinnati or Little Rock. I look forward to the same thrill listening to voices from across the country and around the world……
Thank you for your time, and for the wonderful website.
Thank you, John, for your question and for the kind compliment!
I’m publishing this question here, though, in hopes the SWLing Post community can help you. I have very little experience matching antenna impedance this way especially when transmitting will be involved–there will be a mis-match, I’m pretty sure. With that said, I know many mag loop receive-only antennas actually use RG6. It would certainly be great to use an existing penetration for this application.
Post readers: If you can help John, please do comment. Quite frankly, this isn’t the first time I’ve been asked this question, so I’ll follow comments as well.
John, I’m sure you’ll soon have your radio on the air receiving the world just like when you were nine–or even better! Great choice in that Kenny TS-590SG–it has a brilliant general coverage receiver for broadcast listening!
Thanks for the great comments, it was good news to hear I could use the existing coax. Mario, Yes, I will make sure the old coax connection is clean and wasn’t going to use the signal splitter. cnick6, thanks for the advice on the discone for transmitting purposes. I will look into other antennas, like the Maldol HVU-8, Gap Challenger DX, and the Alpha Promaster Sr.
I still have a lot to learn and it’s great there are fine folks like you out there to help a beginner out. And thanks again to Thomas, for posting this on the blog, and for the great SWLing website.
Sincerely, John
No major reason not to use the RG/6 cable already piped into the house but do get rid of that signal splitter and replace with a well-sealed adapter to link the two cables together. Make sure you clean the end connectors of the old coax if they have been exposed to the elements.
As for discones they are great for wideband reception and depending on the model can be used for transmitting on some of the ham bands so check the specifications. If the antenna covers the CB band you might be able use it for 10m but again check specs and how much power the discone will handle.
A good piece of equipment for the shack is a SWR meter and antenna tuner if transmitting is your plan. Tuners that combine an SWR/Power and dummy load are handy too.
Have fun setting up your antenna.
The TS-590SG is a HF radio only. So the discone is a bad antenna choice. You cannot transmit above 6m with the 590SG just FYI.
…a question for me, too! To say that this Kenwood TS-590 has excellent general coverage, how would this compare to more familiar (dx’ing ) portable radios….eg. CCrane 2E or the (holy grail) Panasonic Rf-2200? For example, if listening from Toronto, I can pick up WCBS (New York City) easily but after 22:00 UTC, the same for WSL (Chicago), Boston, etc,, but how would this expensive rig compare to receive these stations during the daytime hours?….I don’t much care for cable, satellite, Wi-Fi radio transmission, but the real challenge is TERRESTRIAL radio…aka 100 year old technology!….what to think?
I use RG-6 only, so the answer is yes, it can be used. There is no problem with the mismatch between the radio impedance of 50 Ohms, and the cable impedance of 75 Ohms. Make sure there is no splitting of the cable along the way, that is, between the wall outlet and the outside. There will always be some loss the more you splice the cable, but it’s not a show stopper.
Yeah, if you do the maths it works out at ~0.2dB loss per 75-50 ohm transition, for a total of ~0.4dB loss. That’s comparable to the loss you’d get from a pair of good 75-50 ohm un-uns (~0.15dB each, or ~0.3dB total), or a run of RG-8 that’s 15 metres longer (~0.39dB @ 20MHz). Not a problem for reception.
In transmitter-type terms, it equates to a VSWR of ~1.8-1.9:1, or ~8W reflected back for 100W in. Not great, but not a show-stopper. And, lets be totally honest with ourselves here, for any modern transceiver – especially one with an inbuilt ATU, like that Kenwood – even that’s on the edge of worrying about.
RG6/U quad shield is 75 ohm and an excellent lead-in cable for SWL receiving antennas. I use a dedicated run for long wire antennas. RG6/U quad shield coaxial cable is not very expensive and may be purchased at stores like Home Depot in various lengths complete with F connectors. Use F connector adapters and BNC connectors if desired. I’m not a ham and so I will not touch the subject of loading up a TV coaxial cable system for transmitting purposes.
You can use 75 ohm coax even when transmitting, but I wouldn’t even sweat the details where it comes to receiving. http://www.n5dux.com/ham/files/pdf/Yes%20All%20My%20Coax%20Cables%20Are%2075%20Ohms.pdf