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Author Topic: Receive Antennas  (Read 15874 times)
VK6HP
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Posts: 186




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« Reply #15 on: November 17, 2017, 05:13:37 AM »

Apart from the examples which AC7CW and I have given, there's a wide range of theory and practice applicable to active and passive ways of maximizing signal-to noise-ratio in receive situations, as opposed to optimizing (for example) transmit efficiency.  Some of the discussion areas involve the receptors (antennas, a few of which have been mentioned), some relate to RF and analog processing (such as phasing schemes, or even the diversity option mentioned by the previous poster), and some relate to DSP (with a variety of algorithms, including adaptive noise reduction, array beamforming and correlation). No doubt there are other relevant topics arising from practical experience and knowledge.  Many of these are far from esoteric:  for example, I've just been admiring the efforts of a local ham in putting together a very effective ferrite loop system for 160 and 80m.

I again applaud N7GCO's suggestion of a forum and respectfully suggest that, with such obvious "don't know what they don't know" on display, the case for a forum, even as a partly educational one, is strengthened.  Maybe "receive antennas and interference mitigation" covers a lot of ground, with "interference" taken in the broadest meaning.
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K8AC
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Posts: 1770




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« Reply #16 on: November 20, 2017, 06:57:43 AM »

Quote
I again applaud N7GCO's suggestion of a forum and respectfully suggest that, with such obvious "don't know what they don't know" on display, the case for a forum, even as a partly educational one, is strengthened. 

I agree that a forum category on receive-only antennas would be of value.  Presently, I know of no other site that offers a forum for discussing these antennas and the W8JI site is perhaps the only one where you can find info on many types of receive-only antennas in one place. 

To those who have no understanding of receive-only antennas, I'll offer a few comments.  Many of us are what I would call "low band DXers", generally meaning we seek DX on 160, 80 and/or 40 meters, usually on CW.  On 160 and 80, stations from Asia are usually just at my noise level (I'm near the east coast) when listening on typical antennas such as dipoles, verticals, inverted Ls, etc.  Today there is a wide variety of "receive-only" antenna designs that can be used to increase the received signal strength to the point that we can hear and copy the weak stations that we could not copy or even hear with conventional station antennas.  Some of these antennas require vast real estate to implement, while others need almost none.  Which receive-only antenna will be best for a particular station depends on your location, lot size, funds available, your personal goals.

If you want to work DXCC on 160 meters, you can probably do it without a special receive antenna.  If you expect to work 200 or 300 countries on 160, it's safe to say that you won't be able to do it without a special receive antenna - you simply won't be able to dig them out of the noise.  If you live in the southeastern USA where thunderstorm QRN is common much of the year, your challenge will be even greater.

I've operated many DX contests on 160 meters over the years, and have found that even simple and inexpensive receive-only antennas (such as a Beverage on Ground) will allow you to work additional layers of weak DX that you won't even know is there if you are listening on your transmit antenna.  In thunderstorm regions, where you can routinely hear storm QRN from hundreds of miles away, a receive antenna can offer greatly reduced QRN again allowing you to hear stations that would otherwise be buried in the static crashes.  I've found the Beverage on Ground to be particularly effective in that case. 

A dedicated forum here would provide a place to discuss all the options and help an operator select the right solution for his unique QTH.  There have been many new developments in the area of receive-only antennas in the past 10 years or so and all of them are far less expensive than erecting a tower and beam for the higher bands.   
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KG4NEL
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Posts: 508




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« Reply #17 on: November 21, 2017, 07:03:39 AM »

Part of MW/LW forum, maybe?

I'll be in the market for a RX-only antenna next year, probably - I'd like to get back into broadcast-band DXing with the portable setup, and my transmitting antenna of a wire strung up over a tree makes a nice noise collector but not much else down there.
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K8AC
Member

Posts: 1770




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« Reply #18 on: November 21, 2017, 08:04:09 AM »

Quote
Part of MW/LW forum, maybe?

I don't think so, although some of the receive antenna designs would likely work very well there.  I just looked at that forum and it seems to be dedicated to the new bands below the BC band.  You probably are already aware that the receive antennas that work very well on 160m also work well in the BC band for DXing there.  I'm currently using a Hi-Z three element vertical array and used to have a K9AY array as well.  With both of those, I could tune to a specific BC band frequency and hear two different stations clearly depending on the direction the antenna was switched to. 

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K4FMH
Member

Posts: 431




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« Reply #19 on: November 28, 2017, 08:49:01 AM »

Been doing this for over 50 years now...never lost the thrill for BCB dxing! Let me suggest either a Quantum Loop (and perhaps their Phaser unit too) or the new MFJ Rx Loop. The latter is beating the socks off of my beloved Wellbrook 1530+ on MW.

73,

Frank
K4FMH

Part of MW/LW forum, maybe?

I'll be in the market for a RX-only antenna next year, probably - I'd like to get back into broadcast-band DXing with the portable setup, and my transmitting antenna of a wire strung up over a tree makes a nice noise collector but not much else down there.

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