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Author Topic: Short distance communications on 20M  (Read 12445 times)
KE5ZRX
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Posts: 20




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« on: July 27, 2011, 12:42:34 AM »

Hi All,
My question is probably easy for most of you but I'm new to the scene and could use some help. I have a Yaesu 857 both at home and in my work truck. The home location uses a Buddipole while the truck uses a Hamstick, both of them on 20M. Why is it that once I'm more than 3-4 miles from home, I can't hear my wife back at the house? Is it because 20M is only for long range communications and not in town driving? We live in a very hilly/mountainous area but even when I'm at the highest point in town (about 8 miles away), I still can't hear her. We have ARTS activated as well and even it cuts out when I'm about 6 miles away.

Ideally, I'm looking for a band that will operate from 0-300 miles away as I travel into REMOTE locations (we live in Ethiopia) with no other means of contact and need the safety net of "home base".

Suggestions? Ideas? Thanks!

Oh, and if anyone knows how I can change my callsign to reflect my real call sign, I'd appreciate it!
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AC5UP
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Posts: 4413




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« Reply #1 on: July 27, 2011, 03:15:03 AM »

Why is it that once I'm more than 3-4 miles from home, I can't hear my wife back at the house?

20 Meters is notoriously poor for groundwave propagation. At 3-4 miles out you have plenty of signal 6,000 feet over your head, but down on the ground where you need it? Not so much..........

Ideally, I'm looking for a band that will operate from 0-300 miles away as I travel into REMOTE locations

The traditional solution to this involves Near Vertical Incidence Skywave (NVIS) propagation where antennas are arranged to radiate their strongest signals straight up where they're reflected down from the ionosphere in a cone-like area of a few hundred miles. Typical setup would be on 75 Meters using horizontal dipole antennas 10-20 feet off the ground. I can't think of an easy mobile setup that would do this, but NVIS was a common old school mode for short range military communications and a web search should return plenty for you to consider. The new school solution involves satellites. NVIS is fairly reliable, but like anything radio there will be days when no bounce = no talk thanks to a solar flare or your knack for finding a dead spot in the pattern.
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KE5ZRX
Member

Posts: 20




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« Reply #2 on: July 27, 2011, 05:16:28 AM »

Thanks for taking the time to post that helpful answer, when I get home tonight I'll switch from 20M to 75M and give it another go. As for the mobile solution, if need be I can always get another Buddipole or similar to take on the road with me.

I usually carry a Satphone as well but have found that HAM is much easier, much cheaper, and believe it or not, the Satphone can't always get a signal. With both the Sat and the 857 going, I should be in decent shape should I hit the deadspot you mentioned.

Thanks again for the helpful advice!
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WB2WIK
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Posts: 21753




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« Reply #3 on: July 27, 2011, 08:48:46 AM »

75m mobile signals will usually give out pretty fast also; I doubt anyone could rely on "0 to 300 mile" coverage from a mobile on any amateur band, especially using small antennas and low power.

I remember working with Harris RF Communications about 25 years ago, they were setting up HF comms stations in Jeeps (for the Marines, I think) and using very long whip antennas (about 12' long) spring mounted at the rear of the vehicle and "bent over" and clipped to the top of the windscreen at the front of the vehicle, so the whip was mostly horizontal.  The transceivers ran more than 100W (I think perhaps 300W or so) and using a band near 5 MHz they were able to get pretty reliable communications over a wide range of fairly short distances (0-300 mile range).  Of course, that was non-amateur, but "we" now have some privileges on the 60m band in that same part of the spectrum and it might be a good place to try.

But it might take bigger antennas than Hamsticks and it might take more than 100W.

If it were me, I'd try using a variety of bands, starting with VHF for the first 25-30 miles.  The 2m band, with both "ends" running 50W to decent vertical antennas, is pretty reliable for that range even if the "home station" antenna is only up 20-30 feet above ground.  The equipment's cheap, too. Smiley
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WB6BYU
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Posts: 17056




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« Reply #4 on: July 27, 2011, 09:31:05 AM »

There are a lot of issues involved here.

There actually are three propagation modes that you will encounter:

Groundwave requires vertical polarization at both ends, and the distance you can cover depends on the
frequency and output power level.  Maximum expected distance is perhaps 50 miles with 1kW on 80m
and 5 to 10 miles on 20m.  In this mode the signal is propagated along the surface of the ground, and
the attenuation depends on the earth characteristics:  I suspect the range will be very short in Ethiopia
due to poor soil conductivity unless the path is over salt water.  Antenna height isn't critical.

Spacewave is the traditional VHF "line of sight" mode - it propagates directly from one antenna to the
other, possibly reflecting off the ground.  The antenna polarization has to be the same at both ends
for maximum signals, and getting one or both antennas higher in the air will extend your range.  This is
the intended mode for CB communications, for example, and will work best at the high end of the HF
range, and on up into VHF.

Skywave is propagation via the ionosphere.  In this case you will see the term NVIS (Near-Vertical
Incident Skywave) because the ionosphere is so high up that the optimum radiation angle is well
above the horizon.  This gives good signal strengths with practical portable antennas - as long as
you are operating on a LOW enough frequency that the signals will reflect from the ionosphere
instead of passing through off into space.  You can use the Local Area Mobile Prediction (LAMP)
plots from the Australian Ionospheric Prediction Service to find the optimum frequency for a given
distance and time of day:

http://www.ips.gov.au/HF_Systems/7/1/9

The "common wisdom" is 40m during the day and 80m at night, but it varies with time of day, season,
and the state of the sunspot cycle:  in most cases you will need different frequencies for day and
night use.  Rarely does the critical frequency go as high as 10 MHz, and right now we often need to use
160m to talk around the state.  Vertical antennas are NOT a good choice (at least for distances out to
100 miles or so) because they have an overhead null, while low dipoles can be quite effective.


So you have three modes to choose from, which will involve different frequencies and antenna
choices.  This topic has often come up in these forums, and the verdict has been that there ISN'T
a single band that will give you the coverage you want regardless of the ionospheric conditions.
Probably the closest you would get would be 6m SSB with a high beam at the base station and
horizontally polarized antenna on a portable mast for the mobile, though that might still have a
maximum range of 100 to 150 miles, depending on local conditions.
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N1LO
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Posts: 1101


WWW

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« Reply #5 on: July 27, 2011, 11:10:49 AM »

1st problem: both antennas need to have the same polarization for local groundwave comms. The usual propagation for long distance radio contacts is via skywave.

Your mobile hamstick is vertically polarized. For the best GROUNDwave distance, use a vertical antenna as high as possible at home. Reorient the buddipole at home as a vertical and try again.

Next, you find out that groundwave comms don't really carry that far, and that incoming skywave signals will clobber the ground wave signals.

Good Luck,

- - · · ·  M A R K · N 1 L O · · · - -
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KE5ZRX
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Posts: 20




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« Reply #6 on: July 27, 2011, 12:37:32 PM »

A lot of what was said was a bit over my head but I'm not a lazy person so rest assured I'll be researching all of it. I did understand the polarization though, thanks for explaining that a bit more in detail. Overall though, it sounds like 300 miles is a bit of a pipe dream unless I'm able to switch frequencies and stop to switch antennas on the truck as well.

Since it sounds like NVIS is the best bet, any recommendations for antenna's that I could take with me and set up on the side of the road? Would a G5RV work or is 6 ft. too low? Am I better off getting another Buddipole?

Thanks again!
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WB6BYU
Member

Posts: 17056




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« Reply #7 on: July 27, 2011, 12:58:48 PM »

Quote from: 4671HYBRID
A lot of what was said was a bit over my head...

That's because it isn't a trivial situation and there is no simple answer.

Trying to explain everything in detail in one post gets pretty long.  Feel free to ask questions about specifics.


Quote
Overall though, it sounds like 300 miles is a bit of a pipe dream unless I'm able to switch frequencies and stop to switch antennas on the truck as well.

A screwdriver antenna can change bands without stopping the truck, and there are other options as well.
Generally you can choose one band for daytime and one for night, so you don't have to stop very often.

But for NVIS you'll probably find that an external portable antenna works better than a mobile whip.


Quote
Since it sounds like NVIS is the best bet, any recommendations for antenna's that I could take with me and set up on the side of the road? Would a G5RV work or is 6 ft. too low? Am I better off getting another Buddipole?

I use wire dipole kits:  simple to put up, cheap, no tuner required.  You can put two (or more) dipoles on a
single feedline so you don't have to switch antennas when you change bands.  Especially on the lower
bands (40 / 80 / 160m) the full-length wire will run rings around most shortened antennas.

Height is good, but you can still make contacts at 6' off the ground.  If you can get the center up 24' on
a mast and tie the ends off at half that height (using long ropes down to ground level if needed) then
there isn't a lot to be gained by going higher, at least on 80m.  I've tied up my dipoles in lots of less-than-
optimum situations, such as along the top of a barbed wire fence, flagpole, or between two rocks with the
center propped up 3' off the ground on a stick.  For vehicle operation I often use the military mast sections
that come in 4' pieces - I can easily set up a 32' mast by myself.  If all you have available is a couple
broomsticks connected with short lengths of plastic water pipe, you use what you can.  For backpacking
I don't bother taking an antenna support, other than my walking stick, but I tend to be in areas with
enough trees that I can find something to hang it from.   Something like #22 stranded, insulated hookup
wire makes a small kit but still handles 100 watts with ease, and likely is something you can make from
locally available materials.
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KZ1X
Member

Posts: 3330




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« Reply #8 on: July 27, 2011, 12:59:14 PM »

You may find this article to be of interest:

http://www.antennex.com/preview/Folder03/Sep3/mob_ob.htm


The guys in the VK outback have similar type requirements, and their real-world solutions could be adapted to your needs.
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K2OWK
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Posts: 1273




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« Reply #9 on: July 27, 2011, 01:59:29 PM »

I would use a 75 meter inverted "V" at the base. This will eliminate the polarization problem (inverted "Vs" are both). A properly tuned antenna on the mobile is important. With that being said 300 miles of reliable communications is a dream, it will not happen. With a good set up running about 100 watts during good conditions you can expect ranges from 50 to 100 miles, but not all the time. Daylight hours would be the best time. Night would be the worst because of noise on this band. The commercial station I used a number of years ago operated on 4460 MHZ. From ship to shore with 100 watts output we had a constant range of 100 miles during the day and about 20 miles at night. During land operation we could work about 50 miles during the day and about 15 miles at night. The base had an inverted "V", and the mobile had a top loaded whip vertical.

Hope this helps.

73s

K2OWK 
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W0FM
Member

Posts: 2080




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« Reply #10 on: July 27, 2011, 02:15:18 PM »

You also asked:  "Oh, and if anyone knows how I can change my callsign to reflect my real call sign, I'd appreciate it!"

Go to the left hand column here on eHam.  Click on "eHam Help (FAQ)"  Your question is answered near the top of the page that opens.

73,

Terry, WØFM

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N1LO
Member

Posts: 1101


WWW

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« Reply #11 on: July 27, 2011, 02:28:23 PM »

Here's a trick that I use for an 'instant' big signal on 80m mobile/portable.

Put a 55-60' piece of #24 wire (experiment a little to find the right length) with an alligator clip on one end and 50' or so of kite string on the other, on a kite string winder and keep it in the trunk.

Pull over anywhere, and clip the wire onto the top of your mobile HF antenna. For a bugcatcher type, put your coil on bypass. For a screwdriver, set it on 10m. The idea is to bypass all loading as you will be clipping on a full-size, 1/4 wave wire that needs no additional loading to resonate on 80m. For a hamstick type antenna, clip the wire to the base stud of the antenna to make the electrical connection, and use a loop of tape or string to hold the wire up at the top of the antenna. You may need a larger battery type clip instead of an alligator clip.

Unwind the radiator and string. You can lay it across low bushes or thread it through low tree limbs. I use a 'slinger': a 6 oz egg sinker on a 3' length or cord with a snap swivel for connecting it to lines. Toss the slinger over or through tree branches and stretch out your radiator. You get the idea: a low, horizontal, NVIS radiator.

Your vehicle has to provide the ground plane/counterpoise. Pursuant to good mobile HF efficiency, you should bond all your body panels, doors, hood, trunk & frame together. You may even benefit from another 66' wire clipped to the vehicle body and stretched out in the opposite direction as the radiator. I haven't done enough testing to confirm how beneficial this actually is.

I have used this same wire to operate on 160m portable, with my mobile HF antenna loading set for 80m.

See my current antenna at http://www.qrz.com/db/n1lo  I have connection points above and below the coil for clipping on low-band extention wires.

GL,

- - · · ·  M A R K · N 1 L O · · · - -
- - - G L O U C E S T E R ·  V A - - -


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KE5ZRX
Member

Posts: 20




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« Reply #12 on: July 28, 2011, 04:39:48 AM »

You also asked:  "Oh, and if anyone knows how I can change my callsign to reflect my real call sign, I'd appreciate it!"

Go to the left hand column here on eHam.  Click on "eHam Help (FAQ)"  Your question is answered near the top of the page that opens.

73,

Terry, WØFM



Thanks Terry, I sent them an email request to change it over for me.

Les, KE5ZRX
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KE5ZRX
Member

Posts: 20




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« Reply #13 on: July 28, 2011, 05:28:07 AM »


I use wire dipole kits:  simple to put up, cheap, no tuner required.  You can put two (or more) dipoles on a
single feedline so you don't have to switch antennas when you change bands.  Especially on the lower
bands (40 / 80 / 160m) the full-length wire will run rings around most shortened antennas.

Height is good, but you can still make contacts at 6' off the ground.  If you can get the center up 24' on
a mast and tie the ends off at half that height (using long ropes down to ground level if needed) then
there isn't a lot to be gained by going higher, at least on 80m.  I've tied up my dipoles in lots of less-than-
optimum situations, such as along the top of a barbed wire fence, flagpole, or between two rocks with the
center propped up 3' off the ground on a stick.  For vehicle operation I often use the military mast sections
that come in 4' pieces - I can easily set up a 32' mast by myself.  If all you have available is a couple
broomsticks connected with short lengths of plastic water pipe, you use what you can.  For backpacking
I don't bother taking an antenna support, other than my walking stick, but I tend to be in areas with
enough trees that I can find something to hang it from.   Something like #22 stranded, insulated hookup
wire makes a small kit but still handles 100 watts with ease, and likely is something you can make from
locally available materials.

Do you have any wire dipole kits that you'd recommend or are they pretty much all the same? And why don't you need to tune them, is it because they're a specific length that corresponds to the frequency?
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KE5ZRX
Member

Posts: 20




Ignore
« Reply #14 on: July 28, 2011, 05:40:45 AM »

Here's a trick that I use for an 'instant' big signal on 80m mobile/portable.

Put a 55-60' piece of #24 wire (experiment a little to find the right length) with an alligator clip on one end and 50' or so of kite string on the other, on a kite string winder and keep it in the trunk.

Pull over anywhere, and clip the wire onto the top of your mobile HF antenna. For a bugcatcher type, put your coil on bypass. For a screwdriver, set it on 10m. The idea is to bypass all loading as you will be clipping on a full-size, 1/4 wave wire that needs no additional loading to resonate on 80m. For a hamstick type antenna, clip the wire to the base stud of the antenna to make the electrical connection, and use a loop of tape or string to hold the wire up at the top of the antenna. You may need a larger battery type clip instead of an alligator clip.

Unwind the radiator and string. You can lay it across low bushes or thread it through low tree limbs. I use a 'slinger': a 6 oz egg sinker on a 3' length or cord with a snap swivel for connecting it to lines. Toss the slinger over or through tree branches and stretch out your radiator. You get the idea: a low, horizontal, NVIS radiator.

Your vehicle has to provide the ground plane/counterpoise. Pursuant to good mobile HF efficiency, you should bond all your body panels, doors, hood, trunk & frame together. You may even benefit from another 66' wire clipped to the vehicle body and stretched out in the opposite direction as the radiator. I haven't done enough testing to confirm how beneficial this actually is.

I have used this same wire to operate on 160m portable, with my mobile HF antenna loading set for 80m.

See my current antenna at http://www.qrz.com/db/n1lo  I have connection points above and below the coil for clipping on low-band extention wires.

GL,

- - · · ·  M A R K · N 1 L O · · · - -
- - - G L O U C E S T E R ·  V A - - -




Thanks for the tip, I'll have to order some wire from the States or see if our warehouse has any over here.


From what I've gathered so far, I should try operating in the 40,60,75, and 80m range, making sure that both antennas are polarized the same (preferably horizontal), and also take advantage of 2m the first 25-30 miles. There was also mention of putting the antenna's as high in the air as possible, does that matter much in mountainous areas like mine where when I'm 40 miles outside of the city, I'm on the other side of the mountain range?  
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