eHam

eHam Forums => Site Talk => Topic started by: N7GCO on October 26, 2017, 10:25:57 PM



Title: Receive Antennas
Post by: N7GCO on October 26, 2017, 10:25:57 PM
I would be helpful if there was a separate category for "Receive Antennas".


Title: RE: Receive Antennas
Post by: KAPT4560 on October 28, 2017, 06:11:59 AM
 Which band? Those receive-only questions could possibly be answered in the SWL section?


Title: RE: Receive Antennas
Post by: PLANKEYE on October 29, 2017, 11:38:47 AM
Well if you plan on transmitting or receiving you need a antenna. Not sure I follow your logic. 


Title: RE: Receive Antennas
Post by: KD8IIC on October 30, 2017, 08:39:07 PM
  Plank; Re - Read OM, he gave you the correct answer.
  Receive antennas was your post's topic, nothing said about transmitting antennas.


Title: RE: Receive Antennas
Post by: N2MG on October 31, 2017, 06:25:59 AM
I understand the request and sympathize with the idea.

A "Receive" antenna  (Beverages, etc.) is a special case and deserving attention, but breaking up the current Antenna etc.  forum category further is not without its downside. 

We can think about it!

73 Mike N2MG


Title: RE: Receive Antennas
Post by: PLANKEYE on November 03, 2017, 01:02:23 PM
Ok maybe I missed something but any antenna you buy or build from a book will receive something hopefully depending on what antenna it is ETC...  I mean throw up something in the air, put up some wire people are writing books on the best antenna designs.  I think the ARRL has a couple of antenna books out on how to make your own.  If all you want to do is receive you have it made you can put up a clothes line, hook your coax to your eve spout ETC... You don't want to TX on that eve spout though.  Lets take a look at the heavier design that will tolerate 1500 watts of power, it will receive just as good (way better than your eve spout)  if used as a receive antenna only and now you have the best of both worlds.  The only difference between a RX only antenna and one you can put some power through is the RX only antenna you can't put some power through it. 

Listen on the air an have fun.   


Title: RE: Receive Antennas
Post by: N2MG on November 05, 2017, 11:15:31 AM
Look up Beverage antenna


Title: RE: Receive Antennas
Post by: W9BB on November 08, 2017, 05:09:01 AM
For a lack of space (like most of us), try the FLAG antenna.


Title: RE: Receive Antennas
Post by: WB4IVF on November 08, 2017, 09:55:11 AM
Some basics on receive antennas:

https://www.w8ji.com/receiving_basics.htm

I think a separate receive antenna category is a fine idea.

Howard


Title: RE: Receive Antennas
Post by: VK6HP on November 10, 2017, 09:58:05 PM
Hello Mike and all,

I think a "receive antennas" section would be useful.  As well as the traditional techniques (Beverages etc), there's now considerable additional interest in small, active antennas (loops, whips, ...) for noise reduction, especially in urban areas.

It would be useful to broaden it a little and also give a home to discussions about allied signal processing - RF, analog and digital.  I have in mind various RF phasing schemes, and baseband analog/digital array processing. As time goes on, and digital correlation-based processing becomes more feasible and common, the topic can only expand.

73, Peter.


Title: RE: Receive Antennas
Post by: N0YXB on November 11, 2017, 05:13:22 PM
I think a "receive antennas" section would be useful.  As well as the traditional techniques (Beverages etc), there's now considerable additional interest in small, active antennas (loops, whips, ...) for noise reduction, especially in urban areas.

It would be useful to broaden it a little and also give a home to discussions about allied signal processing - RF, analog and digital.  I have in mind various RF phasing schemes, and baseband analog/digital array processing. As time goes on, and digital correlation-based processing becomes more feasible and common, the topic can only expand.

73, Peter.

Whether or not a new forum is created I hope discussions like these do occur.


Title: RE: Receive Antennas
Post by: AC7CW on November 12, 2017, 08:49:15 AM
I really do think that a receive antenna forum is in order. It would help amateurs to improve their technology and that is in the spirit of [not to mention the legal definition of] the hobby, no?


Title: RE: Receive Antennas
Post by: KD8IIC on November 16, 2017, 07:33:56 AM
  how does not a length of common wire, preferably strung outdoors, away from power line and digi
  cable noise and an antenna tuner suffice?
  don't think there's all that much to it or much to be
  mystified about to the point of having a forum page for this one topic.


Title: RE: Receive Antennas
Post by: AC7CW on November 16, 2017, 07:58:04 AM
  how does not a length of common wire, preferably strung outdoors, away from power line and digi
  cable noise and an antenna tuner suffice?
  don't think there's all that much to it or much to be
  mystified about to the point of having a forum page for this one topic.

Noise rejection, ionospheric condition vs takeoff angle, switching of antennas, rotating loop antennas, rotating loop arrays, directional arrays, grounding, HOA restrictions, aesthetics... 


Title: RE: Receive Antennas
Post by: KAPT4560 on November 17, 2017, 01:41:47 AM
 Every October I go to a cabin in Letchworth Park for a week of R&R. It is at the high elevation end of the park during the off-season. The gorge and fall foliage is spectacular. Peace and quiet.  ;D
 I bring a couple of National NC and Hammarlund boatanchors with me for company. A couple of 100' spools of 16ga. stranded copper wire from the auto parts store is cheap and can be strung through the trees. Keep it high so that hunters or hikers won't walk into it by accident. I bring an AC outlet tester to be sure that the wiring and ground at the cabin's outlets are correct. The CFLs come out and I install incandescent bulbs for my stay.
 I can hear things in the countryside that I can't hear in the city. QRM is very low here. It is like fishing, you can never tell what you will pull in next. Longwave reception is outstanding in the wee hours along with coffee and doughnuts.
 I have read the ARRL Antenna, older Radio Amateur handbooks and other SWL tips/hints books. I have tried dual-diversity antennas where one signal may fade and the other picks it up for no loss of reception.
 'How it works' knowledge is useful, but experimentation is the key. Try to keep the longwire high and dry and away from large objects. Try an E-W and N-S orientation to see what works best. The slope or inverted-L may give some omnidirectional coverage. A good ground can be important at the lower frequencies.
 A separate Receive Antennas category may be unnecessary for longwires, loops and Beverages. Your questions or experiences should be welcome in the SWL section. If you are battling noise, the RFI/EMI sections are helpful.


Title: RE: Receive Antennas
Post by: VK6HP 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.


Title: RE: Receive Antennas
Post by: K8AC 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.   


Title: RE: Receive Antennas
Post by: KG4NEL 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.


Title: RE: Receive Antennas
Post by: K8AC 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.