ARRL 160 & Rx antenna

[Able2fly]

 
Julius,
 
Would you (or anyone) please elaborate on the use  of an Rx antenna?
 
Thanks
Bill  K3UJ
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

This was  the first time I used the Rx Antenna feature
and it was  invaluable.

Thanks to everyone for a great  'test!

73,
Julius
n2wn
K2/100 #3311


 
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[Don Wilhelm-3]

Bill,

Often low efficiency antennas make great low noise receiving antennas -
example is a multiturn loop which can be quite directional, but transmit
efficincy would be almost 'zip'.  Another example is traveling wave antennas
such as the Beverage - which also are directional, but the efficiency is low
and therefore unsuitable for transmitting.

By using the K2 Rant, one can automatically select the Rx antenna on any
band separate from the selection of the transmitting antenna.

This is often used with great success on 160 (and 80 meters) where a low
noise directional antenna is used for receiving and a vertical is used for
transmitting.

73,
Don W3FPR

> -----Original Message-----
>
> Julius,
>
> Would you (or anyone) please elaborate on the use  of an Rx antenna?
>
> Thanks
> Bill  K3UJ
> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>
> This was  the first time I used the Rx Antenna feature
> and it was  invaluable.
>
> Thanks to everyone for a great  'test!
>
> 73,
> Julius
> n2wn
> K2/100 #3311
>
>

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[Ron D'Eau Claire-2]

It allows you to use a separate antenna for receiving. Often such an antenna
can provide a superior signal-to-noise ratio than the "main" antenna,
especially if you're using a vertical for transmitting. I have a wire a
couple of feet above the ground running along my fence that often provides
superior reception over the doublet up high, especially on the
lower-frequency bands where QRN is more of an issue. QRN, especially
man-made QRN, is less pronounced down near the ground.

Of course, such an antenna has a lot less "gain" than a wire up high, which
means it's not so good for transmitting, but gain is not a concern in
receiving on the HF bands. The rig (especially the K2) has far more gain
than necessary to overcome the losses in almost any antenna. So the whole
story is in the signal-to-noise ratio. The better the S/N ratio, the better
your K2 will hear, regardless of the gain of the antenna.

Some dedicated people have even built underground doublets, letting the
ground shield them from QRN while signals, although attenuated, are cut much
less allowing them to hear signals their huge skywire up high couldn't
detect.

Of course such underground antennas are well insulated from the earth, often
placed inside water-tight pipes.

Other options are to use a small rotatable loop that allows you to null out
QRM and peak the signal.

Just because a transmitting antenna hears as well as it radiates does not
mean that it's optimum for receiving!

Ron AC7AC

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of [hidden email]
Sent: Tuesday, December 06, 2005 5:27 Pme
To: [hidden email]; [hidden email]
Subject: [Elecraft] ARRL 160 & Rx antenna


 
Julius,
 
Would you (or anyone) please elaborate on the use  of an Rx antenna?
 
Thanks
Bill  K3UJ
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

This was  the first time I used the Rx Antenna feature
and it was  invaluable.

Thanks to everyone for a great  'test!

73,
Julius
n2wn
K2/100 #3311


 
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[Bill Coleman-2]

On Dec 6, 2005, at 8:27 PM, [hidden email] wrote:

> Would you (or anyone) please elaborate on the use  of an Rx antenna?

The fundamental problem on the low bands is the high noise level. A  
good transmitting antenna can often have S6-9 noise, or worse. It's  
hard to hear weak signals with all that noise.

As W8JI would put it, the characteristics of a good transmitting  
antenna and a good receiving antenna aren't the same. A transmitting  
antenna should have gain in a particular direction (and angle) in  
order to place the most signal into the target area. For receive, at  
least until you get into the upper VHF region, gain isn't really  
important. The problem is noise -- you can pick up the ambient noise  
on the band with barely any antenna at all -- all that gain just  
brings more noise into the radio.

For receive, the important thing isn't gain, but antenna pattern. An  
antenna with a good pattern will ignore noise (and QRM) from  
directions outside the target area. Less noise means better signal to  
noise ratio. Signals that aren't audible on the transmitting antenna  
are then audible on the receiving antenna.

There are many designs for effective low-band receiving antennas.  
These are quite lossy, having gain 20-30 dB below that of a  
transmitting antenna. Examples include Beverage antennas, Flags,  
Pennants, EWEs, K9AY loops. Despite being lossy, they can have quite  
sharp patterns, especially the Beverage antenna.



Bill Coleman, AA4LR, PP-ASEL        Mail: [hidden email]
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901

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[Mark J. Schreiner]

Bill and others,

The explanations by Don & Ron were as always right on and very helpful.  
I already knew the answers but enjoyed reading the replies anyway.  I
still have questions, though, too, so please continue to read on (we get
there eventually).

I would like to point out a couple of resources for more info on the
topic.  First is a book by John Devoldere, ON4UN called "80m DXing",
oops, sorry, I'm showing my age, it is now called "Low Band DXing" or
"Antennas and Techniques on Low Band DXing".  I did a quick Google
search and guess I should pick up a more up to date version of the
book.  The copy I have is from 1978 and was an excellent resource at
that time.  Recently looking through it some info is obviously dated
(comparison of different radios now considered to be "vintage" although
still excellent rigs even compared to today's newer radios, such as the
Drake R4B/C, Kenwood TS820, Collins  S-Line/KWM2, Signal One CX7,
Collins R390, Heath SB101, etc) while other information is timeless
(theoretical and practical info on the antennas for the most part as
well as operating practices).  It gives lots of great info on these
subjects with practical examples from a time honored expert.

Another book that is about 10 years newer for the copy I have which is a
2nd edition, although it looks like the latest release that is still
available is the 3rd edition, but I'm not sure when it came out, is
called "The Beverage Antenna Handbook" by Victor Misek, W1WCR.  This
book includes topics on single wire Travelling Wave Antennas & multiple
wire Steerable Wave Antennas.  As is the case for most ham related books
it is mostly practical and only moderately theoretical.

Both of the above examples require a bit of real estate, or at least a
cooperative neighbor.  I convinced my neighbor at one time that the wire
I proposed to run out onto his property was only used for Rx and I
guaranteed to him that *it* would not cause interference.  This
negotiation worked and my neighbor and I still have a good relationship
to this day (long after I've moved away, although my moving away is not
the reason for our good relationship these days!).  I've seen other
installations that have also taken advantage of a "good neighbor
policy".  Try it, it works!

Other Rx antennas that are popular lately and work almost as well
without nearly as much real estate which you should be able to find more
info on the web include the EWE Array or K9AY loops.  I'm currently
investigating the latter along with a small magnetic loop (oh, I thought
it was small for 160m at about 12' diameter, maybe I should make it
smaller yet!).

Okay, now for the questions that I have.  Having recently worked several
stations surprisingly easily with my K2 at 5W during the recent Top Band
contests (both the ARRL as well as the less active QRP ARCI a few days
before) I am intrigued with possibilities of a Rx Only antenna.  I know
the old saying that "You gotta hear 'em before you can work 'em" surely
applies, however, I think that especially when running QRP the station
on the other end has much more work to be able to hear your signal, so
they need to likely have an even better Rx station than you have.  There
were several stations which I couldn't work that had moderate (not
strong and not weak) signals during this past weekend.  Maybe if they
had better Rx antennas I could have worked them.  I tried several
different times hoping that conditions maybe had improved.  Generally
this was on Friday night while at my QTH Saturday night didn't seem as
good.  However, my questions (finally) are these:  If I have a great Rx
only antenna won't I be able to hear many more stations that I probably
won't be able to work?  Okay, so there is a possibility that some of
those stations will also have great Rx antennas and so between the two
of us we may be able to work where previously I may not have been able
to hear (and hence work) them.  But does anyone have any experience with
this and care to comment?  I'm not trying to gather this information to
discourage the attemps, just looking for some practical experience on
this as part of a "reality check".  I have only so far worked one
European station and heard very few on 160m, but my experiences on 160m
with the K2 are just beginning.  The guy I worked in Greece was using a
1000' Beverage for the USA (one and the longest of 4 that he had total)
and I think was running about 800W.  With my Carolina Windom at about
45' that I used on both Tx & Rx I was barely able to copy him initially,
then as his signal finally improved so that I could copy so-so, good
enough to copy his callsign after enough times of him calling CQ or a
few people now and again answering him (while there was several big
pileups a few kHz above).  Finally when I was sure of his call I called
him and he came back and fairly quickly the QSO was in the logbook!  I
remember giving him a 559, which was really a bit of a stretch, but he
gave me a 569 even though I was running only 5W compared to his 800W.  
Okay, so with enough stations out there with serious Rx antennas I'll
likely be able to work a few more, if only I can hear them as well, I
suppose, but I'm still anxious to hear any practical experience in this
activity.

I'd also like to add that my most memorable DXing on 160m was while I
was a kid in Michigan (maybe 1983 timeframe) and using an antenna that
shouldn't have worked and today with my experience I would likely not
ever attempt to use it.  However, I didn't know better at the time and
used it anyway.  It was about a 15 to 20' vertical with a large loading
coil about 2/3 of the way up.  Not sure where this was supposed to work
but I put it on a homebrew tripod sitting on a 2nd floor porch and ran a
single #8 or #10 ground wire (Aluminum from RatShack) to a copper ground
rod made of 4 to 6' of 3/4" copper pipe.  With my TS820S at 100W I heard
a large pileup for the Marshall Islands.  Rather than bumping heads with
guys running "real" antennas and probably most running much more than
100W I tuned around a bit figuring that the band should be open to that
area in general so maybe I'd find another station with less of a
pileup.  Sure enough, I found KH6VT on Hawaii and quickly worked him.  
Moments later I found a station I had no idea where he was located, but
there was this voice in the back of my head from my Elmer, K8OT, who
told me "Work 'em first, worry about 'em later" so I worked UV1OO.  I
then reallized it was Franz Josef Land (look it up if you don't know
where it is, I didn't originally!  Hint, it is in the Barents Sea east
of Svalbard and north of mainland Russia).   Wow, what awesome
conditions, and working them back to back in different directions with
an antenna that wasn't supposed to work!  I shut off the rig and went to
bed with happy thoughts rather than risking an attempt to work yet
another DX station and possibly not getting through.  Boy, times have
changed as I would take that risk today if I heard such great band
conditions while using an antenna that "should" work and my trusty K2
running QRP.

Sorry for the *really* long email.  Just wanted to offer some
encouragement & possibilities for one of my favorite bands (especially
now near the bottom of the solar cycle).  CU on 160m!

Mark, NK8Q
K2 4786


[hidden email] wrote:

>
>Julius,
>
>Would you (or anyone) please elaborate on the use  of an Rx antenna?
>
>Thanks
>Bill  K3UJ
>  
>
>
>  
>

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[Julius Fazekas n2wn]

Hi Bill,
The idea behind a Rx antenna is to provide some
direction (Front to Back) and or null offending noise
sources.

Where it is difficult to have a 4 element 80M yagi at
120', it is possible to have a beverage, loops, phased
short verticals or other type antenna. This antenna
generally makes it easier to hear the other station.

My transmitting vertical was VERY noisy compared to
the Rx antenna. It makes all the difference between
hearing DX or QRP stations and thinking you're all
alone on the band.

On 160 and 80, the difference can be quite dramatic.

The Elecraft module lets you have a seperate antenna
without playing the switching game outside of the rig.
Plus you get 160!

Hope this helps.
73,
Julius
n2wn

--- [hidden email] wrote:

>  
> Julius,
>  
> Would you (or anyone) please elaborate on the use
> of an Rx antenna?
>  
> Thanks
> Bill  K3UJ
> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>
> This was  the first time I used the Rx Antenna
> feature
> and it was  invaluable.
>
> Thanks to everyone for a great  'test!
>
> 73,
> Julius
> n2wn
> K2/100 #3311
>
>
>  
>

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[Vic K2VCO]

J F wrote:

> The idea behind a Rx antenna is to provide some
> direction (Front to Back) and or null offending noise
> sources.

I built a ferrite loop antenna for 160, and it is much quieter than my
inverted L.  See

<http://www.qsl.net/k2vco/ferriteloop/ferriteloop.html>

...at least, look in a few minutes -- QSL.net appears to be down right now!

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[Bill Coleman-2]

On Dec 7, 2005, at 12:17 AM, Mark Schreiner wrote:

> If I have a great Rx only antenna won't I be able to hear many more  
> stations that I probably won't be able to work?

Yes.

I wasn't running QRP in the ARRL 160m contest, I was running a full  
100 watts from the K2/100. Still, there were several stations I could  
not contact, even though they had pretty good signals into my area.  
W7SE in WY was one of them. I heard him both nights, and spend  
several minutes calling him, but barely got any response from him.

There's certainly a danger in being a "rabbit" station (All ears, no  
mouth) when you use a good Rx antenna. The thing with the low bands  
is that it is usually the noise that limits what you can work. Guys  
will hear you, but you won't be able to copy them. (In retrospect,  
maybe some of those guys are running QRP....)

> With my Carolina Windom at about 45' that I used on both Tx & Rx I  
> was barely able to copy him initially, then as his signal finally  
> improved so that I could copy so-so, good enough to copy his  
> callsign after enough times of him calling CQ or a few people now  
> and again answering him (while there was several big pileups a few  
> kHz above).

Some 15 or so years ago, when Packet was very, very new, I remember  
logging in to a local packetcluster node and seeing spots for  
stations on 160m. I switched to my 300 foot long, 15 foot high random  
wire and tried to chase some of the spots. I tried several, but could  
hear nothing. Finally, I saw one spot with the notation "LOUD!!!".  
This guy, I could just barely hear.

My problem wasn't that I needed a good receiving antenna -- I just  
needed a good 160m antenna. That Carolina windom may be a pretty good  
compromise all-band antenna, but its not going to be very effective  
for 160m, particularly at just 45 feet high. (That's what 13m?)

So, while it may be interesting and educational to put up a receiving  
antenna, my advise to you would be to try and put up a more effective  
160m antenna. One of the more popular simple antennas is the Inverted-
L. 140 feet of wire, running vertically as high as you can and then  
horizontally. Fed against as many 100 foot (or so) radials as you can  
lay down, it would be a pretty effective antenna.

Horizontal antennas aren't that effective for 160m. W8JI has made a  
long study of this. In addition to several verticals, he also has a  
300 foot high full size dipole for 160m. 300 feet may seem high, but  
consider that it isn't even 90m tall. It's just over 1/2 wavelength  
high -- which is where dipoles start to become really effective  
antennas. Tom has related that he almost never finds the dipole to be  
more effective than the verticals for DX, except for some really  
oddball openings around sunrise.

The key dimension for any horizontal antenna is the height above  
ground in wavelengths. That Carolina windom probably started to  
really shine on 20m and higher. It's just not practical to place 160m  
antennas this high. Hence - verticals.

> It was about a 15 to 20' vertical with a large loading coil about  
> 2/3 of the way up.  Not sure where this was supposed to work but I  
> put it on a homebrew tripod sitting on a 2nd floor porch and ran a  
> single #8 or #10 ground wire (Aluminum from RatShack) to a copper  
> ground rod made of 4 to 6' of 3/4" copper pipe.

That's the thing about antennas -- EVERYTHING WORKS. Even dummy loads  
can be used to make contacts. But you'll work a lot of stuff a lot  
easier with more effective antennas.


Bill Coleman, AA4LR, PP-ASEL        Mail: [hidden email]
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901

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[Julius Fazekas n2wn]

 However, my questions (finally) are these:
> If I have a great Rx
> only antenna won't I be able to hear many more
> stations that I probably  won't be able to work?

Maybe not many more, but certainly more if your Tx
antenna is lacking. That would be the case no matter
your power level.

Okay, so there is a
> possibility that some of
> those stations will also have great Rx antennas and
> so between the two
> of us we may be able to work where previously I may
> not have been able
> to hear (and hence work) them.  But does anyone have
> any experience with
> this and care to comment?

Sure, my previous 160M setup I used the vertical for
Rx and Tx. I though I worked KL7 (an very hopeful ESP
QSO) but it wasn't solid and I doubt he really worked
me. Using a decent Rx antenna and the same vertical, I
now have a solid QSO. I heard 8Q7 on 80M with a Rx
antenna, just could crack the pileup with 100W and
keep my rate up. Propagation is a big factor. Many
DXpeditions report one way propagation, and I'm sure
you've experienced it as well when someone is booming
in, yet hears few if any SS.
 
The guy I worked in

> Greece was using a
> 1000' Beverage for the USA (one and the longest of 4
> that he had total)
> and I think was running about 800W.  With my
> Carolina Windom at about
> 45' that I used on both Tx & Rx I was barely able to
> copy him initially,
> then as his signal finally improved so that I could
> copy so-so, good
> enough to copy his callsign after enough times of
> him calling CQ or a
> few people now and again answering him (while there
> was several big
> pileups a few kHz above).

This is great DX, sounds like propagation was on your
side most of all. Timing is everything as well, that
window of opportunity may only have lasted 5 to 15
minutes!

Catch you in the next one...
73,
Julius
n2wn
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