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Author Topic: vertical antennas  (Read 96177 times)
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AE1CT
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« on: May 28, 2011, 10:57:35 AM »

will vertical antennas work on am or is a dipole better. what about inverted v antennas? a friend of mine told me that a may pole vertical is a very good antenna to use on am....any thoughts on this topic.
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« Reply #1 on: May 28, 2011, 11:42:24 AM »

For 75M "local" work within 400 miles or so, a flat, straight dipole at 40' high (or more) is the best antenna you can get.  Feed it with coax or openwire - it makes no difference in performance except for band-hopping with the openwire.

An inverted vee is a close second, but a compromise because the legs start to cancel radiation as they come closer together. The average height is reduced too.

A vertical will be down maybe 15-20 db locally compared to the dipole. On 160M, va ertical can work well, but is still down to a dipole for local work.

Keep the dipole as far from large objects as possible, like houses, powerlines, etc. Trees are OK and almost invisible. The geometry of the dipole is important. No zig-zags or sharp angles. Strive to make it look like a "T" with the feedline coming straight down to the ground, if possible.  Your radiation pattern will then exhibit the best figure-8 pattern possible. Be sure to erect it broadside to your two favorite directions. (Southwest - NE for example)

Build your own and avoid the gimmick antennas offered for sale. A simple dipole with one center insulator and two end insulators fed with feedline is all you need.  Try to support the center. It will last longer in wind storms. Use 3/16" "aircraft" braided cable to go thru the tree limbs on each end. Rope will break after a short time due to friction from wind.

Do you have the room to erect a full-size 123' dipole for 75M?

Hope this helps.

Tom, K1JJ
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AE1CT
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« Reply #2 on: May 28, 2011, 12:11:02 PM »

i dont have very tall trees in my yard (30 ft) high and the most room i have is probably 40 meters and i want to get on 80. i want to operate mosty sw from my location and there are no trees that will give me that direction. i want to get on the air but im in a position were i dont have a big yard or the tree hight that i need. WHATS a future AMer to do. any ideas would be greatly helpful.
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« Reply #3 on: May 28, 2011, 12:19:23 PM »

In your situation, the next best thing would be to hang a 123' long 75M dipole at 30' high. Stretch the flat legs out as much as possible (65' ?) and then drop the ends down towards the ground on each end. Pull the ends out as far as possible making a slope if you can.  This dipole will look like an inverted "U".  

At 30-40' high, the dipole is mostly omni-directional for local work anyway, so don't worry about the supports and directions for now.


This will work fine on 75M and also on 40M if you wish to feed it with openwire.  Some of the AMers do this and have great signals.   You can even load it up on 160M if you use heavier wire and good quality openwire.  Go to Home Depot and pick up a 500' spool of #10 or #12 black electrical insulated wire. Make the openwire and flat top from it and use a balanced antenna tuner for all band use.  If you use coax feedline, no tuner required, but you are limited to just 75M with the antenna as described.

T
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AE1CT
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« Reply #4 on: May 28, 2011, 12:33:38 PM »

i was told that i can use a long wire and run it from tree to tree and feed it with 400 ohm ladder line and run a short 20 ft lenght on the open side of the ladder line, sort of like a windom. i mostly want to operate 40, 80 and 160 AM.  will this work for me with some reasonable results, im not looking to be a power house, i just want to be heard and have some fun on AM.
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« Reply #5 on: May 28, 2011, 12:49:23 PM »

Sure, anything will "work" and you will get many opinions.  Some of the guys run Windoms with excellent results.

But it's hard to beat the proven design and performance of a balanced dipole as I described. 

Receiving the other guy is half the battle as well as being heard when QRM and conditions get rough. Do all you can to get that antenna up as straight, flat and balanced.  A simple dipole is hard to beat.

Well, back outside for some more work... I'm black out.

T
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« Reply #6 on: May 28, 2011, 03:39:06 PM »

The usefulness of Verticals is highly dependent on local ground conductivity.   At my present QTH in Tyler, TX they work great because of the very high local ground conductivity,  At my "other" QTH in the mountains of New Mexico they are a waste of time due to the poor ground conductivity.

Dipoles are OK, but require 2 or 3 supports and if they are high enough to work DX off of the sides, they are dead off of the ends.  Not particularly a good plan if you only have one antenna.

Personally I prefer inverted V's for low band work.  They only require one support, are fairly forgiving of installation irregularities (like not having the two sections in line) and are generally omni-directional.   Here I'm blessed with several 60 -70 foot pine trees and have a 75M Double-Bazooka inverted V with the center up about 50 ft in a pine.  It "used to be" abt 60 feet up in the center but the support rope broke and the center dropped to about 50 ft and but stayed up so I've just left well enough alone.   

Not having tall trees to work with, the commonly available military surplus 4 foot fiberglass mast sections can be used as an economical center support for 40 or 50 ft before they get too wobbly.  If you pull the legs of the V out with around 120 degrees of separation you can get away with one guy.

I usually join or listen to the "Texhoma Traders Net" on 3890 on Saturday mornings and find that I generally can copy a greater percentage of the check-ins than most anyone else with my inverted V. 

Also, obsessing on making a dipole "flat"  is pointless and maybe even counter-productive.  Dipoles are installed in all sorts of configurations, V's, slopers, flat tops, bent on the ends.... what ever fits the available supports will work reasonably well.   The theory that they have to be flat and straight to work is a bunch of hogwash.   The higher it is in the center, the better it will work for DX.

Another popular approach to 160/80/40 is a full wave loop for the lowest band. feed with balanced line.   Whatever shape the available supports allow will work, but the closer to round the better.  I haven't tried one of these but a lot of hams swear by them.  Most people I've heard using one of these have them at 30 to 50 feet.

Copper house wire is heavy,expensive, and prone to stretching.  Copperweld is a better, cheaper, wire for antenna use. 
 
See http://www.thewireman.com/antennap.html 

73 Jack KZ5A
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« Reply #7 on: May 28, 2011, 04:26:37 PM »

Quote
Also, obsessing on making a dipole "flat"  is pointless and maybe even counter-productive.  Dipoles are installed in all sorts of configurations, V's, slopers, flat tops, bent on the ends.... what ever fits the available supports will work reasonably well.   The theory that they have to be flat and straight to work is a bunch of hogwash.   The higher it is in the center, the better it will work for DX.


Here we go again.

ANYTHING  will "work".  But compared to what?   The standard is a flat, straight dipole. Any departure from this is a compromise. Model it and see.

As we lower the legs of an inv V, they start to cancel radiation. Bring them down below 90 degrees apex angle and your input impedance starts to drop - continue to lower them until we get no radiation at all as the legs  become parallel as a feedline.  Also, the average height goes down as the legs are dropped and the take-off angle goes up.  Add a reflector or director and the front-to-back ratio (and gain) gets poorer with inverted V elements compared to flat  dipoles.

Why do they make Yagis with flat elements? They could use inverted V’s if they desired. But flat dipole elements are the best performers over ground, that’s why.

BTW, slopers are possibly the worst use of a dipole for DX work. They radiate off the sides better than in the direction of the slope. Surprise, surprise… that’s how dipoles are supposed to radiate – broadside.  Slopers were a big thing in the 80’s on 75M before the DXers wised up and went back to high dipoles or Yagis.

OK, I realize we are splitting hairs here and the guy looking for advice will probably end up with some wire hung in the trees somehow, but that’s no reason not to teach him the best method first. Maybe he had the perfect supports to put up a flat dipole, maybe not.  If we have to use inv v, or inverted U’s or whatever to get a dipole in the air, so be it.  But to tell the guy that striving to make a dipole flat is pointless and counter-productive (and hogwash) is ridiculous.

Tom, K1JJ


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« Reply #8 on: May 28, 2011, 05:00:14 PM »

Amen to your rebuttal, Tom.

Walt
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« Reply #9 on: May 28, 2011, 05:06:16 PM »

<<<Another popular approach to 160/80/40 is a full wave loop for the lowest band. feed with balanced line.   Whatever shape the available supports allow will work, but the closer to round the better.  I haven't tried one of these but a lot of hams swear by them.  Most people I've heard using one of these have them at 30 to 50 feet.>>

Then you should try one.  I have.  Loops suck unless you can get them way high, higher than most hams are able to do.   If you have four or more really tall trees, as in over 100 feet, then go for it.  Lower down on 75 there is too much wavelength exposure and ground loss through coupling to earth and on 160?  Fugeddabodit, unless you can get the loop up around 150-200 feet on that band.  

Somewhere on one of his pages, Cebik said small and high (high dipole) beats big and low (loop at 30 or 40 feet) any day of the week.   Don't make the mistake of thinking that because of its size, a loop is a great performer.  Height is everything.  Height directly = dBs and is really the only legal way to get a lot of them but, height is expensive.   Therefore, if you can only afford one or two 50 foot supports, you are far better off going with a dipole than several short poles holding a loop.  

On a dipole it is okay to let the ends dangle down if you have to.  But, there is a big difference between the ends hanging and an inverted V.  I have a 130 foot dipole on my 100 x 50 foot lot with 20' on each end hanging down (dipole is at 50').   I  don't have the big signal I'd like to have (few of us do) but I can usually make contacts and it is much better than the 1 w. loop I had on 75 at 25 to 30 feet before.   You will be amazed at what a simple high dipole can do.   Most of the big AM signals on 75 are from guys who have nothing more than dipoles up around 100 feet or more.   If you didn't know you'd swear they were running 2 kw broadcast rigs.  But they are often running no more than 300 w., sometimes much less.   Antenna is everything.
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« Reply #10 on: May 28, 2011, 08:25:45 PM »

    I had to cut down my skyhook 90' pine tree. That left me with nothing to support a high dipole/inverted "V" for 80M. In desperation I installed a Hustler 5BTV with a tilt base and radial plate from DX Engineering. Also pinned 40 25' radial to the grass.
    Result: If I can hear 'em, I can work 'em. And I can hear a lot.
No it's probably not as good as a dipole overall, but in some ways it's probably better. It does have some downsides: Expensive. Labor intensive. Has to be precisely tuned. No wiggle room on 80M.http://amfone.net/Amforum/index.php?topic=27315.msg208313#msg208313
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« Reply #11 on: May 28, 2011, 08:59:02 PM »

Verticals work fine over poor ground if you use elevated radials. My 160 and 80M DX results from this hilltop rock pile speak for themselves.

Verticals on high ground got a bad rap in the early days of AM BCB because the poor ground and on ground radials destroyed the surface wave part of the lobe. It took over 75 years for the FCC to get away from their 1920's mind set and authorize elevated radials.

Carl
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« Reply #12 on: May 28, 2011, 09:07:04 PM »

I agree with Carl.  I put up a Zero Five elevated ground plane for 40 through 10 a couple months ago.  It's doing FB on those bands with my tuner.  15 meter AM into Europe and all over the world in other modes much easier than my inv vees.

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« Reply #13 on: May 29, 2011, 10:11:55 AM »

..what's a "zero five" ?....never heard of it...

..sk..
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« Reply #14 on: May 29, 2011, 10:45:23 AM »

..what's a "zero five" ?....never heard of it...

..sk..

http://www.zerofive-antennas.com/

I build my own wire antennas, but I couldn't build an aluminum tubing vertical as good as Tom @ Zero Five. 

The version I have uses a 26 foot radiator and 6 ridged aluminum radials 100 inches long.  The radials are above my roof line.  It's designed to work with a wide range tuner via a 5kw matching transformer for 40 through 10 meters.  It works better than anything I had up for the higher bands.  I wanted a simple elegant antenna since we are heading towards a peak in the cycle.  Beams and rotors are beyond my present finances.

I still use my 80/40 meter parallel inv vee for 80/40 "local" work.
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« Reply #15 on: May 29, 2011, 11:00:40 AM »

..ok john...i had a cushcraft r-7 yrs ago..it had some kind of matching box near the base...40-10, but it sucked...had to guy it with poly rope as well...i was very disappointed with it...as i understand, you werk nights, or operate in the wee hours on the morning...i'm likely going on a 3-11pm shift (eastern time) in the next month....what time/where do you operate mostly?..

..tim..

..sk..
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« Reply #16 on: May 29, 2011, 11:01:00 AM »

Verticals are cool antennas to look at. Must be the old AM broadcash influence in us... Wink

Yes, as we all know, the ground plane, whether it be in the form of a car, ground radials or elevated radials is the key to vertical performance.  I suppose we could say that otherwise, a vertical is a vertical is a vertical. The difference being the loss in traps or of a severely shortened vertical. Though, W2FMT? showed us that shorties on 40M with big capacitance hats did quite well for efficiency.

Many of the guys (including the previous posts) report outstanding results on 40M and higher with verticals.  160M and 75M DXing works well too. Though, the anomaly appears to be when using a vertical for "local" AM work on 75M. Out to maybe ~300 miles, in general, I've never seen a vertical stronger than a dipole. This 300 mile range on 75M is of utmost importance to AMers, at least on the east coast. The high angle radiation can be down as much as 20db compared to a dipole.

Farther away, W9AD has proven how well verticals work on 75M using his phased array of Hygain? towers.

What I'd really like to see is someone try a 4-square of verticals, even 1/8 wave whips, on the higher bands, put out in a clear field away from everything. There are a few phasing boxes available (Comtech and DX Engr?) that are plug and play. The ability to see f-b, forward gain and directional changes with those low angles when using a good ground plane would be quite versatile. I still think a high Yagi would be hard to beat, but a 4-square could be installed with much less cost and effort, depending on the ground system used.

I agree that the Earth soil plays an important part into how elaborate the radial system needs to be. The elevated radial debate has been interesting over the years.

Chris, AJ1G, was talking in another thread about yesterday driving his car mobile out on Stonington Point, CT (next to the ocean) and using 5 watts  20M CW to work Europeans easily. It wud be an interesting experiment to see the difference when he drove inland 10 miles and tried the same thing.

T
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« Reply #17 on: May 29, 2011, 01:09:24 PM »

What is the alleged magic about the 43' vertical on 160? Huh  I hear a lot of people, even those with plenty of space to erect something taller, report that's what they are using. Some operate with a good radial system and some without.  Obviously, performance will be much improved with the good ground system, but so would increasing the height to at least 1/8λ, approximately  65'.  Even with top loading and a good radial system, as the vertical length is decreased below 1/8λ, radiation efficiency drops off rapidly.

43' on 160 would be equivalent to 10'9" on 40m, barely more than an 8' mobile whip.
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« Reply #18 on: May 29, 2011, 02:09:31 PM »

"i'm likely going on a 3-11pm shift (eastern time) in the next month....what time/where do you operate mostly?."

Tim, It isn't easy finding AM activity during dark hours in Summer.   75m (no antenna on 160) noise floor is 20 to 30 over S9 where most AM signals are... (except maybe Don KYV or Brandon IIA) into my location.  Makes it difficult copy.  On 40 I do play on 7290 and call CQ a lot to no avail between midnight and dawn.  Sometimes on 7.160 but there are a lot of VK's and ZL's around there on sideband, so I often don't bother firing up AM.  

The way my job works is I get 3 nights off in a row so I am occasionally up in the early afternoons, but not too often.  When I am I could be anywhere between 40 and 6 meters on the usual AM frequencies for each band.  

The best success I've had running AM in the early mornings (dark hours) during static season is with scheds.  Paul VJB and I hooked up one morning, that was fun.  

"What is the alleged magic about the 43' vertical on 160? "

From http://www.hamradio.me/antennas/answer-to-everything-43-feet-antenna.html

The peak radiation angles and relative antenna gain for each bands are:

    ~ 5 dBi @ 57° for 10 meters – impressive, but high angle
    ~ 4 dbi @ 37° for 15 meters
    ~ 1 dBi @ 16° for 20 meters – nice low angle
    ~ 0 dBi @ 25° for 40 meters
    ~ -2 dBi @ 29° for 80 meters – this is quite functional
    ~ -8 dBi @ 23° for 160 meters – lossy, but it does work

Several things are apparent:

    The antenna has “better than nothing at all” performance on 160 meters and is certainly interesting for this difficult band.....................


I think the stats there and that last statement says it all.  It will load up and put out a signal on 160 but it is certainly a compromise there.   Don, the fact that you actually hear people using them proves it does do this, but pretty poorly.  My elevated ground plane (26 ft radiator) actually loads on 80 m and puts out a signal a bit poorer than my low inv vee.  If I had no 80 m antenna, I could use it and make contacts.  Maybe come winter, It will do better for real long distances, but I doubt it.  I'll do A/B comparisons then.
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« Reply #19 on: May 29, 2011, 03:32:21 PM »

Interesting stats, John - tnx for posting them!

What stands out is the "gain" on 10-15M is in the higher angles. 20M is perfect at 16 degrees however. Ever hear someone say, "Boy, I sure would like to fly a 400' high balloon wire as a vertical on 75M."   Your stats are a good example showing how the pattern gets moved into the higher angles just like a 160M Zepp acts on 20M... the desirable ½ wave pattern goes to heck.

The optimum angle on 20M for east coast to Europe is around 15-20  degrees take-off or so. On 15M it's about 10 degrees and on 10M about 5-7 degrees. This all varies with sunspots and conditions, of course, but studies have shown on average, a Yagi stack designed for these angles works well overall.

So, there is a reason to use a 1/4 wave or 1/2 wave long vertical on the band of interest. That's when the angle is lowest  - and also the IR efficiency is higher compared to a shortie version.

Another thang to consider is, "Can my location SUPPORT" a low angle of take-off?"   If you do the geometry, to support a 15 degree vector angle coming off an antenna, it takes quite a distance on the lower bands. On the higher bands, it still means the area around the antenna must be clear of major obstructions like houses, power lines, etc to be optimum. If the lobe needs to go thru a close-by house, the plumbing, wiring, etc may make it down many db compared to the higher angle lobes that clear the house.

The word, "optimum" is the key. Installations will still work, but not as well when radiation has to propagate thru structures to cover the lower angles. RFI is another symptom of low angles in neighborhoods.

Also, especially for horizontal DXing antennas, can the location’s EARTH soil support the lowest angles 1000’s of feet away?  Radials will not help these very low angles when they attempt to reflect off the ground and reinforce the main lobe.

Verticals are very demanding systems and jealously guard their territory. The best installation is to mount them out in a clear field with nothing for a mile around. But few of us can pull this off.  Here, I not only have tower obstructions, but my Earth soil is rocky and poor. High horizontals are all I can work with… sigh.  I would love to try a 4-square  or even 8-square on  40M and 10M, but the results on the other bands was poor.

The exception was a 3-vertical phased system I built for 160M using about 15,000’ of radials. That vertical system took out a dipole at 190’ into Europe by 10db. Verticals indeed work well on 160M if they have big radial fields to work with. Plus the optimum angle on 160M for Europe is MUCH higher, like maybe 25-30 degree or higher.  BUT, the wavelength distance is longer, so we still need a minimum of obstructions to clear even a 30 degree takeoff angle.

No free lunches or everyone would be doing it already…  Grin

T
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« Reply #20 on: May 29, 2011, 03:50:12 PM »

..ok john..i'll let you know how my shift is gonna werk out. i shud be home about mid-nite,(eastern), or so when i go on this shift. i'm not one to go to bed when i get home, hell, it's like going to bed at 4 in the afternoon for the day-lighters...40 might be a good go...whatcha think?..we shud keep in touch on this...
..tim..

..sk..
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« Reply #21 on: May 29, 2011, 11:36:00 PM »

What you almost never hear or read anyone say or write when it comes to using a vertical, is that they almost always tank big time on receive.
On 75 m. it's just about impossible to operate at night with my vertical (which is the only good time to use one since they are a low angle skywave antenna above 160 m.) if I have to use it as my rx antenna.   Only way I can use it is with my small tuned 75 m. rx loop.   On the high bands, they take a dump on rx as well--I'm not sure why, maybe the S/N ratio up there also, as I have never been able to hear well with one.  

Maybe out in the sticks they are okay on receive but mine always picked up too much noise and even on a quiet high band, a balanced horizontal antenna like a dipole snagged the signals much better.   I have gotten by on 160 with the inverted L on tx and rx but there, the 160 m. tuned rx loop is often a QSO saver.

What is the alleged magic about the 43' vertical on 160? Huh  

They magically suck in wads of cash from people with boatloads of $$$ and thimbles of antenna knowledge.  
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« Reply #22 on: May 29, 2011, 11:57:29 PM »

The 43 feet is a 5/8 wave antenna on 20m. I don't know why anyone would claim that it could be very efficient on any band lower in frequency. The same logic was used with the G5RV. It was not intended as a multi-band antenna. It is a gain antenna on 20m only.
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« Reply #23 on: May 30, 2011, 11:50:45 AM »

The problem with using a vertical for receive is caused by the same characteristic that makes it a good DX antenna for TX and a good AM broadcast transmitting antenna.  At certain lengths it is predominately a low angle radiator - good for DX.  But it also responds well to ground wave, which is inherently vertically polarised.  Much, if not most, local electrical noise propagates by ground wave, so a vertical is an extraordinarily efficient receiving antenna for electromagnetic smog.  Much of the time I can't receive worth a hoot with my 127' vertical on 160.  The dipole, beverage or indoor loop usually work better for RX. When transmitting with a vertical, you really do need a separate receiving antenna.
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« Reply #24 on: May 30, 2011, 12:37:07 PM »

Much of the time I can't receive worth a hoot with my 127' vertical on 160.  The dipole, beverage or indoor loop usually work better for RX. When transmitting with a vertical, you really do need a separate receiving antenna.

Yep.

Almost without exception, the big gun 160M DXers use a beverage for receiving and a vertical for transmitting. It's almost a given up there.

It works that way on 75M and 40M too, but to a diminishing degree.  Maybe that's because the average noise level drops until there is virtually none on 20M and higher.  Ie, many guys use their verticals for receiving above 160M.

I notice the DXer guys with the 4-squares on 75M sometimes complain that the noise is killing them, but their bevs are fine. Then other nights they listen better on the verticals. Much must depend not only on local noise, but propagated noise via the ionosphere and their antenna's directivity abilities.

I notice on certain nights the f-b of the 75M high loops will enable me to hear Europe thru the USA western storms to the back.  That extra couple of S units gives quite a receiving edge some nights when many guys throw in the towel.     F-B is a good thang when needed..

T
Logged

Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
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