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Author Topic: HF Receiving Antenna Myths  (Read 12242 times)

Offline Barycenter

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HF Receiving Antenna Myths
« on: May 04, 2014, 1819 UTC »
I'm new to this community and only have started up my interest in HF SWLing since the late 1970s. One thing I do know (being a scientist/engineer) is that there is a prevalent misconception on antennas for receivers vs. transmitters. Most books and online sites talk about tuning antennas to the proper length/configuration to reduce loss from reflection/impedance etc. for transmitting power.

However, this is not true for receiving antennas. In order to tune a receiver you must reverse the concept. Even if a halfwave dipole is 'tuned' by length to the correct frequency, the power or gain in your receiver depends on the impedance of your feed line and receiver input. Definitely not the same.

That said, I would like to hear other's opinions on this subject and what you have found to be the best HF antenna-receiver combination and why. Do you agree with this myth?

Thanks!
Central MN
Airspy HF+ MLA-30+
Yaesu FT-891 - MyAntennas EFHW-4010
Sony ICF-SW7600GR - Par EF-SWL

QSLs would be nice! Send to: pluraldon [at] yahoo.com

Offline BoomboxDX

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Re: HF Receiving Antenna Myths
« Reply #1 on: May 06, 2014, 1147 UTC »
I don't really understand all that much about impedance matches and all that.  I understand a big impedance mismatch can cause issues with transmitting.

The only transmitting I did was on sideband CB, where I built a quad loop that was tuned to the sideband portion of the CB band, and it worked very well at a low SWR.

That quad also worked well for VHF Low Band skip. Whether this was due to the quad being cut for a nearby frequency range (27.3 mhz) or because of its directionality, I don't know. I'm guessing it was a combination of both.

For just receiving, the only 'tuned' antennas I've used were air core loops for MW DX. Obviously, they have advantages over a wire -- unless the wire is very long.

For SW, I have used wire antennas of varying lengths, and had the best reception with a 100 ft. wire that was orientated to take advantage of the local terrain -- although I've had good reception with shorter antennas also.

The only thing I ever needed an antenna tuner for was to reduce images on my single conversion Realistic DX-160.
« Last Edit: May 06, 2014, 1148 UTC by BoomboxDX »
An AM radio Boombox DXer.
+ GE SRIII, PR-D5 & TRF on MW.
The usual Realistic culprits on SW (and a Panasonic).

Offline Muskrat

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Re: HF Receiving Antenna Myths
« Reply #2 on: May 08, 2014, 0726 UTC »
For many years the only antenna I had was eighteen turns of magnet wire wrapped around a 18" square box about 4" deep.  The turns were in slits spaced about a 1/2" apart with two turns in each slit.  That was about a total of 120' of wire.  For over four years this antenna performed very well for me.  For the last thirty years I have used a 55' random wire in my attic end fed with rg59 with good results.  I also have a home-brew Slinky dipole strung on paracord.  My next antenna will be a home-brew T2FD.
« Last Edit: May 09, 2014, 0025 UTC by Muskrat »
Grundig Satellit 800, Grundig 450DLX, DX 440, Icom R70, 55ft random wire, built-in telescoping antennas, home-brew Slinky dipole. Central Indiana.
Please send QSLs to muskrat39@hotmail.com

Offline mondomusique

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Re: HF Receiving Antenna Myths
« Reply #3 on: May 11, 2014, 2343 UTC »
Hi Barycenter:

Last summer while camping I used a Global AT-2000 antenna coupler (tuner) between a Tecsun PL-600 portable receiver and a 50ft random wire to listen to the 49 and 22 meter bands.  I was able to peak the received signals by turning the tuning knobs on the AT-2000.  This brought up the received level of signals I wanted to listen to, made the stations 'pop up'.  

The summer before, I went camping with a Palstar R-30A radio and 40 ft random wire connected to the Hi-Z antenna terminal of the Palstar, no antenna tuner, listened to the same bands.  I was surprised how quiet my reception was, stations were not popping out even though I was in the middle of nowhere.

I'm not a scientist, but it seems that an antenna tuner works as advertised for shortwave listening with a random wire antenna.

I'm planning on going camping this summer with a random wire, Global AT-2000 antenna tuner, Afedri SDR and laptop.  Perhaps I will 'see' the signals 'pop out' as I dial the tuner.

Would like to hear about others' take on usefulness (or not) of antenna tuners for receiving.  

Afedri sdr, Palstar radio, Wellbrook antenna
Location: Halifax, Nova Scotia, Canada
eQSLs: djprincehifi@yahoo.ca

Offline Skipmuck

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Re: HF Receiving Antenna Myths
« Reply #4 on: May 12, 2014, 0009 UTC »
I have been using an MFJ-901B Versa Tuner for several years. I've used it from 1986-1989, and having returned to shortwave listening after 24 years, have been using it since August of 2013. My antennas have always been random longwires of various lengths and I have found the tuner to be an excellent way of getting the most from the longwire! When tuning from let's say 6925 KHZ to 21460 KHZ, I have to radically change the settings on the MFJ. I've actually checked the effectiveness of the tuner by removing it and hooking the longwire directly to the NRD-515....some frequencies are attenuated and others aren't. I firmly believe it works well for matching a longwire with a receiver. Before the NRD-515 I used it with a Yaesu FRG-7 and it also worked in a similar fashion.
QSL's to poorbrookking >at< aol.com are greatly appreciated! All reception and postings using My radio, My antenna, and generally in real time(excluding posting of SSTV images!).
QTH:Springfield, MA
JRC NRD-515 with 43 meter half wave dipole into MFJ 949E Versa Tuner: also Grove SP-200 & SONY 2010's

Offline CaptnKliegle

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Re: HF Receiving Antenna Myths
« Reply #5 on: June 05, 2014, 1735 UTC »
There's nothing better than a properly tuned, resonant antenna, for the desired band of operation.
That said, one of the manual tuners from MFJ or similar can be used to get a proper match. i.e. Rotate the L and C knobs for maximum noise on the receiver.

At Field Day, we run home made monoband beam antennas out of aluminum fed directly to the TXR's. Trying to use the 20M beam on ANY other band is like beating a dead horse, the SWR will be out to lunch and the band will appear to be dead except for the few signals way in excess of S-9.

As far as end fed wires go, there are numerous sites on the web for suggested lengths. Here's a pdf file to look over and see which length you can accommodate:
http://www.balundesigns.com/Wire%20Lengths%20for%209-1%20ununs.pdf

I'm using on of his unon's (9:1) on my SDR-iq remote servers. I get emails occasionally from users complementing me on the setup.  :)

73 de Kriss  KA1GJU
Seacoast of NH  RXR's =3 X SDR-iq's, 1 x SDRPlays, and 11 AirspyHF+'s . TXR's = 2 X TS-590S,  ANAN200D, 2 x IC-7300's, IC-7610, 2 X IC-7100. Antennas = Resonant wire dipoles, 120' end fed wires, or 2 X SteppIR 3 ele beam @ 70' fixed NE/SW directions. Also host Remotehams.com servers (RX/TX) as well as SDR Console servers V3.xx (RX Only) too!

Offline Antennae

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Re: HF Receiving Antenna Myths
« Reply #6 on: June 07, 2014, 1709 UTC »
2 weeks ago I was messing around with my new adjustable inverted V. I have 5' of bare wire on each end so I can roll them up to shorten or unroll to lengthen the dipole.  I checked the resonance with a noise bridge.  At the longest dipole length, it was resonant to 6.4xx mHz.  At the shortest length it was resonant to 7.470ish and there was an American radio station nearby just barely legible. (so I figure this is as good as the antenna should get theoretically) It was 4pm in the afternoon and sun was high.  I went and checked my horizontal loop (about 97' in diameter) and the reception was the same.   Later at night on the loop the reception came in way better as the sun went down. But I couldn't compare to the inverted V because I took it down. I used my portable receiver on both antennas. It was a case of propagation. 

Nella F. is a forum member and believer in propagation as the main factor in receiving a signal.

This morning I put a tuner on my loop.  My loop connects to a 75ohm coax cable with no balun and comes inside the house.  I found a carrier signal on 6930usb (a slight tone above the noise) and I was able to tune to get better signal and reception than when bypassing the tuner (by about 10-20 percent). So I'm stoked for tonight, hopefully there will be some pirates to listen to and tune up.   
California Coast
Antenna: random wire