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Author Topic: antenna for fm and sw dx eton g3  (Read 4564 times)

Offline acl12

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antenna for fm and sw dx eton g3
« on: January 08, 2012, 1805 UTC »
Hi. I live in a block of flats in England and want to significantly increase my potential for dxing using the eton g3. I cant have outside antennas other than maybe hanging an aerial off my balcony during summer months. What sort of antenna would fit this model and would one antenna serve both sw and Dx purposes. Thanks.

Offline mondomusique

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Re: antenna for fm and sw dx eton g3
« Reply #1 on: January 08, 2012, 2337 UTC »
I would just listen on headphones at night using the built in whip antenna until you know what you can receive.  The G3 should be good as-is for lots of interesting reception, as lots of shortwave broadcasters aim their antennas toward Europe.  Other than that, I would do a lot of reading about equipment and propagation, World Radio TV Handbook (WRTH) from the library would be a good place to start.

If you really want to try an add-on antenna, a slinky antenna located in your flat might work okay with your G3, they are not expensive check Ebay.  The best antennas for urban/suburban locations are made by Wellbrook (a UK company) but they cost a fair bit.
Afedri sdr, Palstar radio, Wellbrook antenna
Location: Halifax, Nova Scotia, Canada
eQSLs: djprincehifi@yahoo.ca

Offline acl12

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Re: antenna for fm and sw dx eton g3
« Reply #2 on: January 09, 2012, 1405 UTC »
Thanks. I will check out what I can recieve 1st and then maybe go for the slinky.

Offline Lex

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Re: antenna for fm and sw dx eton g3
« Reply #3 on: January 10, 2012, 0339 UTC »
You can try a simple random wire dangled out a window or off the balcony.  But if your area is like mine - suburban, apartment complexes and private residences and some businesses nearby - you'll eventually tire of the harsh buzzing RFI.  It's practically unavoidable due to street and parking lot lights, businesses with large lighted signs, neighbors with plasma TVs, and being surrounded by hundreds of poorly shielded electronic devices that contribute to a heavy fog of white noise.

So far the best compromise I've found for suburban DXing (or listening to weak local signals) is a small loop.

Take a peek at the cheap, easy to make Villard homebrewed loop:
http://www.hard-core-dx.com/nordicdx/antenna/special/reducin1.html
http://users.erols.com/k3mt/hla/hla.htm

That design is intended to supplement, not replace, the whip on a portable.  If it offers any improvement at all with your radio on medium wave and shortwave, you might then try a more sophisticated homebrewed loop such as the KR1ST:
http://www.kr1st.com/magloop.htm

My own indoor homebrewed loop is similar to the Villard design, only made from coaxial cable looped around a closet door, rather than foil or copper tubing supported on a tripod or other freestanding support.  I used mine for a couple of years as a passive loop with my Palstar R30C, which has high sensitivity so a pre-amp wasn't necessary.   I was generally satisfied with this until local RFI became intolerable.  The large loop didn't have a sharp enough null.

Then I reconfigured it by adding a small pickup loop, also made from ordinary TV coaxial cable.  This helps me null out the worst nearby offenders - flickering parking lot and streetlights.  However the smaller pickup loop necessitated an amplifier.  I already had a cheap amplified antenna that was popular during the 1990s.  It mostly amplified indoor RFI so I rarely used it.  However, I bypassed the high impedance input for the built in whip, and used only the low impedance feed with shielded cable.  Even though it's not a very good quality amp, combined with the reconfigured loop it was a significant improvement over the passive loop.

Keep in mind that you'll probably get better results with a random wire slung outdoors on certain frequencies and at certain times of day or night.  For example, my local RFI has very little effect above 10 MHz.  So I get better reception with random wire strung along my ceiling for listening to broadcasts and hams above 10 MHz.  And local RFI is usually much less intrusive late at night after neighbors are asleep, and early in the morning.  So a bit of random wire is occasionally better than the loop when local RFI isn't a factor.
That li'l ol' DXer from Texas
Unpleasant Frequencies Crew
Al: Palstar R30C & various antennae
Snoopy: Sony ICF-2010
Roger: Magnavox D2935
(Off-air recordings.)
Email=my name at hotmail dot com

Offline acl12

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Re: antenna for fm and sw dx eton g3
« Reply #4 on: January 10, 2012, 0501 UTC »
Thanks. This looks like a good option. Everytime I touch my antenna it improves reception so supplementing the whip and hanging the loop outside my window should be worthwhile. Will this work for fm dxing as well.

Offline Lex

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Re: antenna for fm and sw dx eton g3
« Reply #5 on: January 10, 2012, 0626 UTC »
Thanks. This looks like a good option. Everytime I touch my antenna it improves reception so supplementing the whip and hanging the loop outside my window should be worthwhile. Will this work for fm dxing as well.

FM DXing is a whole nuther area of expertise.  I've tried it a few times when conditions were favorable, just using a portable and the whip antenna.  So far my best catches were some FM stations several hundred miles south of me near Houston.  But I haven't tried it with any special antennas designed for FM DXing.

Improving shortwave reception with portables requires some experimenting.  Half the time I can't remember the differences between capacitance, inductance, reactance and flatulence.  So I'm not sure why touching the whip antennas on my Sony ICF-2010 and little Panasonic deadens the signal, while touching the whip on my Magnavox D2935 portable improves the signal.  Maybe the Magnavox just really, really likes the way I handle its whip.  :o

Both the Sony 2010 and Magnavox D2935 also respond differently to supplemental antennas.  My homebrewed loop works well with the Sony but doesn't do a thing to improve the Magnavox, which is already very good just on the whip.

Another indoor antenna I tried briefly was shaped like a miniature T2FD, which probably behaved more as a loop than a dipole because it was so small - only about 10 feet long and 2 or 3 feet wide.  It was suspended horizontally from the ceiling, and fed via ordinary shielded audio cable with alligator clips attached to the wire and a miniature mono plug into the antenna jacks on the portables.

I've been intending to try an indoor flag, pennant or ewe type antenna.  I've seen some YouTube demonstrations of these by some UK based MW DXers and they seemed to be getting good results with those designs indoors.  If you Google those antenna types you'll find lots of diagrams and discussions.
That li'l ol' DXer from Texas
Unpleasant Frequencies Crew
Al: Palstar R30C & various antennae
Snoopy: Sony ICF-2010
Roger: Magnavox D2935
(Off-air recordings.)
Email=my name at hotmail dot com

Offline ChrisSmolinski

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Re: antenna for fm and sw dx eton g3
« Reply #6 on: January 10, 2012, 1423 UTC »
I've been thinking off and on a bit about what might work well as a restricted/limited space/indoor antenna.  I stepped back and considered the basics:

If you have a wood framed structure with no large metallic materials, it should be mostly transparent to RF. If you're inside a structure, and that structure has significant metal (in the framing, insulation, or siding), it is going to act somewhat like a faraday cage. It will tend to block RF from outside, including the signals you want. I know that they're using metal studs in some residential construction now, and some insulation has a foil on one side. Those could cause significant shielding. It won't affect RF from inside, which probably includes the signals you don't want (RFI from appliances and such), so you'll still pick up your plasma TV.

One common rule of thumb (from a shielding point of view, where you're trying to keep RF inside a box, say for meeting RFI regulations) is that openings should be less than 1/20th of a wavelength. Note that this is a rule of thumb, not a hard number. For 6925 kHz, a wavelength is 43 meters, so 1/20th is 2.2 meters or 7 feet. So it sounds like a very large window may allow RF at that frequency to get in. It seems to me that if you have to keep your antenna entirely inside, putting it as close to (or on) a large window might help. I'm even thinking about running a loop around the perimeter of the window.

If you can get your antenna outside, that should help immensely, even if it is a small antenna. You're likely to pick up more of the signal of interest, and less RFI from inside. Of course if you have local RFI issues (like the streetlights and commercial signs Lex brought up), you're going to pick those up.

I'm fortunate to live in a rural area with a bit of land, so I've been able to install quite a few antennas over the years, of different types. I still can pick up RFI from various sources including neighbors' appliances, and things here in the house.

One thing that has become obvious to me is that loop antennas offer significant noise reduction as compared to dipoles and other antennas. I'm not referring to a loop that you can rotate to null out specific sources of interference, but a loop that is fixed in orientation. I'm not sure exactly what is going on, but my current line of thinking is that the loop tends to reject relatively local sources of RF because they induce common mode currents in the antenna that get cancelled out.

I've compared the loop antennas (I have a 132 ft T2FD that doesn't tilt as much as it should, and a 635 ft sky loop antenna that is at various heights around the yard between roughly 15 and 40 feet) to dipoles cut for individual bands. The dipoles produce stronger signals, but the noise levels are also much higher. The signals from the loops are lower, but the signal to noise ratios are fat better. To the point where I've discontinued use of the dipoles. The sky loop generally outperforms the T2FD except at very high frequencies, say 20 MHz and up. It's to the point where I almost exclusively use the sky loop.

Now, a 635 ft loop is obviously not practical for the apartment dweller, but it does make me wonder whether loops in general are the way to go (Lex mentioned that his best compromise is a small loop). The next question is, can anything be done to further improve things?

I feed all of my loop antennas with a balun. I find significant noise reduction, vs just connecting the coax to the ends of the loop. This might be a good test to try.

Getting the loop outside might be the next step. Could it be run around the outside perimeter of a window, in a relatively unobtrusive way? (This might not work well if the building has aluminum siding)
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
NRD 545 / netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 670 ft horizontal loop / 500 ft northeast beverage / 58 ft T2FD / 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop

Offline acl12

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Re: antenna for fm and sw dx eton g3
« Reply #7 on: January 10, 2012, 2011 UTC »
I will start experimenting with some of your suggestions. It's a shame that so many stations id like a chance to recieve are drowned out by China radio who operate on high kws and have many foreign transmitters. I'm saving up for an eton 750