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HIGH SWR Tribander




 
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flintstone mop
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« Reply #25 on: August 05, 2005, 08:03:24 PM »

OK Folks here are the results from an installed connector on a 150 foot run of coax going to the Cushcrap A3S

40M 7121 1.7:1 SWR  Rs40 Xs 20
       7290  3:1 SWR    Rs 26 Xs 59    160kc BW?

20M 13.99 2:1SWR    Rs 62
       14.09 1.3:1 SWR Rs 55
       14.300 2.5:1 SWR Rs 19 Xs 11
       14.286 2.5:1 SWR Rs 21 Xs 11

15M 21.100 1.5:1 SWR Rs 41 Xs 15
       21.370 2:1 SWR    Rs 50 Xs 34
       21.450 2.5:1 SWR Rs 30 Xs 33

10M 27.928 1.7:1 SWR Rs 47 Xs 27
       28.5     1.5:1 SWR Rs 54 Xs 12
       28.9     2:1 SWR    Rs 36 Xs 26
       29.2     2.5:1 SWR Rs 20 Xs 11

I guess the next time I'm rich, I'll have the elements shortened to get me  more on the 'phone side /AM of the all the bands. Right now I'm going to run it like it is, unless someone sees the above numbers as waaay out in the left field.
Thanks for looking and I like the new location .
FRED MOP Radio   
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Fred KC4MOP
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« Reply #26 on: August 05, 2005, 11:15:05 PM »

I guess the readings look reasonable, Fred.

Though, the only way to tell what's really happening at the antenna feedpoint is to measure it AT the antena feedpoint OR use a 1/2 wave multiple length of feedline for a particular band/freq.

For example, there is probably a point where you have a 1:1 swr at the ant feedpoint on a particular freq. No matter what length coax you run, you will always see close to the same R and X  at the feedline's end connector on the ant analyzer. [when truly 1:1]

You might  sweep it and look for the 1:1 point. Then add a 1/4 wave coax length jumper [* 0.66 vel factor]  and see if R and X change  a lot. 

So, can you find spots that have 1:1 readings? I just see arbitray freqs listed with 1.5:1, etc,  And how do your curves compare to the published specs?

Yagi swr curves can get complex, not simple like a single dipole. The is cuz as you go up in freq, the director gets closer to the operating freq and lowers the input impedance greatly... and same for going down in freq as the ref gets close. A single dipole's curve is smoother and broader w/o the parasites. But this is where your gain comes from...  generally the closer the els are tuned to the operating freq, the better gain and f-b. But the tradeoff is narrower swr and pattern operating range. All a compromise. 

BTW, with that wooden utility pole... why not add spikes to climb, or bolt on a climbing ladder? You cud do all the work w/o a crane in the future.



T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #27 on: August 06, 2005, 12:13:22 PM »

Thanks Tom VU
I'll have a chance to test with different lengths of coax next week IF IT COOLS OFF.  The best way to check this operation out is to use it and see how the FB ratio is doing for the various bands. I realize that 40M is just a dipole up there.
The utility pole would be very hard for some one to work. A lattice tower enables the climber to strap on to something and work. This pole is pretty fat and the climber would have difficulty reaching around to strap himeslf in.

Has anybody heard of the STEPPir antenna. It sounds pretty neat with the elements continually adjustable from down in the shack. I guess what's up on the tower are hollow fiberglass rods and motors extending and retracting the actual metal elements inside. THey say you can even switch directions without turning the aerial

Fred
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Fred KC4MOP
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« Reply #28 on: August 06, 2005, 01:33:16 PM »

Thanks Tom VU
  The best way to check this operation out is to use it and see how the FB ratio is doing for the various bands. I realize that 40M is just a dipole up there.
The utility pole would be very hard for some one to work. A lattice tower enables the climber to strap on to something and work. This pole is pretty fat and the climber would have difficulty reaching around to strap himeslf in.

Hi Fred,

Well, remember that it's easy to get a good f-b on most any LOSSY directional antenna. Even a loopstick with a tiny whip sense antenna showing -25dbd gain on 75M can show 30 db f-b...  A Yagi that has normal trap losses, water in the connectors and feedline, poor/rusted hardware, etc and 6:1 mismatch swr resulting in a NEGATIVE 10 db forward gain can STILL have a  30 db f-b and clean pattern too. A front to back test is more of a general confirmation that the reflector and director spacing and tuning are in the ballback. That's about all it will tell you.  If you take careful S meter readings using a beacon as you turn it, it will also tell you about pattern side lobes, etc, so you can verify these data against the computer model that it works as it was designed - and there's no other obstructions messing with the pattern. But generally, you will see the sharpest pattern if you can maintain a high Q, meaning connections and parasitic elements are at their lowest losses possible.

Here's my point:

What's hard to do, and is the real test, is achieving FORWARD gain. Everything has to be right to obtain it. Feedline loss, phasing, element lengths/tuning, element IR losses, obstruction attenuation, etc. The only real way to test/verify forward gain is to put up a reference dipole at the same height  in the clear away from the Yagi. If you can see ~5-6 db over the dipole with fast A/B switching most of the time, then you know the Yagi works.  Otherwise, to try to see a 5 db improvement alone by getting S meter reports or by "feel" is futile. An A/B reference is the only way.

As for the StepperIR, I've heard both good and bad. Expensive and remember that the element spacing is fixed, so it is compromised over the full 6-20M spectrum. Lots of moving parts and things to go wrong. I wud go with a log over that any day, OM. Cheaper, reliable and bulletproof. Also each "cell" is optimized for it's own freq.

BTW, bolt a climbing ladder to the face of the pole and add three small ones in a circle at the top and you will simulate a lattice tower.

73,
T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
flintstone mop
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« Reply #29 on: August 07, 2005, 05:18:26 PM »

Hello Tom and  Friends of Radio
I'm gonna try to throw a small switch here at MOP radio and clutter up the  Dining Room with my TS440 and 25 watts  7290AM and give 40M a try on Monday or Wednesday afternoon between 1-3PM . I think I think I remember hearing humans talking during those times.
I'm just curious about the world of radio.  I don't know how I will act when I touch the knobs of something electronic.
I will proceed with other tests Tom has suggested here. I have to install lightning protection at the base of the pole, so there's an opportunity to see what a 65 foot length of coax reads on the MFJ compared to a 150 foot length. If it were proper at the feedpoint then the coax is just a transmission line. With ever changing SWR caused by different lengths,  then the coax is a transformer. (proper thinking here?)
Later........dudes
Fred
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Fred KC4MOP
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« Reply #30 on: August 10, 2005, 07:50:40 PM »

Fred,
How about a T tuner so you can get the swr down at the rig.  Even a series of low Q pi networks could be built for each band. Might be able to add a stub on each band to pull it to 50 ohms.

My log is well below 2:1 except for about 50 KHz around 22 MHz.
it is on R25 guyed every 17 feet. The rotor is half way up the tower with dual bearings. I used a 2 3/8 drive shaft up the middle.  Actually 13 or 14 elements would be sweet.

I was on the tennadyne site this week and now the T12 is 77 LBs up from 56. I had a bunch of emails with the new owner telling him some real feed back from us guys up here in the N.E. (price is over a grand now)
Still has some J.S.es though.

The log was a fun project and the best antenna I've ever used at 6 feed above ground. I had a quad that worked very well but wanted to add warc and was worried about interaction

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Jim, W5JO
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« Reply #31 on: August 10, 2005, 08:31:09 PM »

Probably not Fred.  Even though I don't like Cushcrap, they do a pretty good job with the trap construction.  You might watch for warm spots on the feedline or heating in your transmitter. 

If you have a tuner that will handle the 800 watts PEP, put it in line.  It should absorb the heat for you, that is if it is at the proper point.
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flintstone mop
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« Reply #32 on: August 13, 2005, 11:04:48 AM »

Thanks guys
for all of the inpoot. I'm taking this all in and one fine day there will be a signal once again from MOP radio. The move and retiring and discovering there's a baby on the way have put me through some changes that I have to deal with. I'm not good at changes.  A lot of major changes have happened  to yours truly. Things like retiring and moving and the rest of the lovely new things in my life in a matter of 8 mos. Where a normal guy will do all these things over a coupla years. I'm an O-F who decided to start a life at 58 yrs of age.Plus this DAM heat wave stops all outdoor activities. I fill sorry for you folks near  Washignton DC, MAN it's HOT.
Sorry for my sob story and the bandwidth, but I just appreciate you folks and your guidance as I get back into the swing of things.
PM's are always welcome.
MOPMAN Fred
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« Reply #33 on: August 13, 2005, 12:28:04 PM »

Fred:  Some people call them challenges, others call them opportunities.  Just make the best of everything and you will have a good life  I have a 40 meter kit on my Mosley and when it was installed, I could rotate it against a signal and see when the ends passed the direction of the station.

One thing I forgot to ask.  Is this antenna new or used?  If it is used, did you check the mechanical integrity of the traps?  It is possible, god forbid, that one of them may have a high resistance connection.  My mosley is almost 10 years old and now that I am in my final destination it suddenly has an intermittent connection it seems. 

I thought it was in one of the feeline connections, but the more I look the more I think it is a trap.  The thing has a diriven element for 10/15/20 and one for 12/17.  The 10/15/20 emement seems to vary on the MFJ.  Sometimes it works as it should and sometimes the 20 meter resonance point is 13.850 or so.  When it acts up the 15 and 10 meter bands are out as well with high SWR. 

I have seen the StepIR and it looks like a good antenna, but have never operated with one.  In a corrosive atmosphere it might be a problem in a few years if corrosion builds up.

Good luck.

73  Jim
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« Reply #34 on: August 17, 2005, 10:37:29 AM »

Jim,
I've been doing a lot of reading lately on logs, stacks, etc and of course have come across the StepIR stuff. Seems the guys think highly of them. They are getting quite popular on the air too.   I haven't heard of any serious problems yet. Your concern of corrosion is important, of course. Does the mechanism breath or is it sealed?

BTW, I've decided to take down both of my logs and rebuild them into separate long boom Yagis for 20M and 10M. The bottom one is down already and disassembled. Today I may take the top one down. I removed the bottom one by myself and think I can manage the top one too...

Out of the guts I'm gonna make a  pair of 70'-80' boom 20M Yagis to stack at 60'/120' and something else like that for 10M, I think. Decided that indeed, the logs are a compromise for stacking spacing and raw gain. I never get on 15M or  17M anyway, so it was a waste. I'd rather focus on two bands and have them optimized fully.

That StepIR would be a great antenna to stack a pair.  Not sure if anyone has yet, but would be something.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #35 on: August 17, 2005, 10:40:38 AM »

Gee Tom,
Ever consider selling a log. That was a strapping ant.
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K1JJ
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« Reply #36 on: August 17, 2005, 10:59:58 AM »

Gee Tom,
Ever consider selling a log. That was a strapping ant.

Yeah, Frank,  I did. I was gonna axe $2K for the top one and $1K for the bottom. Considering what Tennadyne charges for their stuff, that's a steal.

But after adding up all the stainless hardware and aluminum I would need to buy again, it was a wash. Stainless has jumped in price big since I bought it before. I'll use everything on the logs and even need some additonal scrap alum to make the new Yagis. The two big 20M Yagis will be mounted on swing gates on the side of the 190'er and manually tied off. Same with the big 10M Yagis. I hate rotators. Fixed/ moveable switching directions are my thang.

I've never had up a set of big long boom Yagis on 20M before... as well as 10M, so wanted to give it a try. The difference over the logs will be marginal, but, a few db is a few db.  Plus, those big logs were starting to scare me as far as working on them. Taking one down is a nightmare with all the guys and those many els. The new Yagis will pull up the side of the self supporter with no guy wires involved. Cake to bring up and down with one person working.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
Jim, W5JO
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« Reply #37 on: August 17, 2005, 11:40:47 AM »

Jim,
I've been doing a lot of reading lately on logs, stacks, etc and of course have come across the StepIR stuff. Seems the guys think highly of them. They are getting quite popular on the air too.   I haven't heard of any serious problems yet. Your concern of corrosion is important, of course. Does the mechanism breath or is it sealed?

BTW, I've decided to take down both of my logs and rebuild them into separate long boom Yagis for 20M and 10M. The bottom one is down already and disassembled. Today I may take the top one down. I removed the bottom one by myself and think I can manage the top one too...

Out of the guts I'm gonna make a  pair of 70'-80' boom 20M Yagis to stack at 60'/120' and something else like that for 10M, I think. Decided that indeed, the logs are a compromise for stacking spacing and raw gain. I never get on 15M or  17M anyway, so it was a waste. I'd rather focus on two bands and have them optimized fully.

That StepIR would be a great antenna to stack a pair.  Not sure if anyone has yet, but would be something.

T

The example I saw at a hamfest used finger stock to make the contact.  It was made by them rather than the ordinary stuff the can be bought off the shelf and was very heavy, so it might wipe any corrosion from the tube.  It would definately work FB for a long time, but as I stated, what about the long haul.  I just don't know.  But from what I observed, it should breath to a great extent.  There were no caps like the satellite guys use over the RG 6 to prevent water from running down the element toward the mast.

Your decision to seperate the antennas is sound provided you seperate them more than 1/2 wavelength which will minimize interaction.  Do you have the room to do that?  Actually more than 1 wavelength would be best, but we do as we have space and money.  With one optomized for 20 and a few KW you will blow the big guys out of the tub.  Good plan.  Same for 10, which is my favorite band, I wish I had the space to do what you are planning.
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K1JJ
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« Reply #38 on: August 17, 2005, 11:57:54 AM »

OK, Jim -

Does the StepIR work with metal tape [like a tape measure] inside a fiberglass tube? So does it actually make contact with a tube? I'm not sure.  I saw one once myself at a ham fest a few years ago. If I had the technology down, maybe I'd build one up. You might try a post on  the "Tower" BB  and axe if anyone has had ANY problems with the StepIR. Esp near the ocean. They will let ya know.

As for the new Yagis...  I plan to build TWO for 20M and stack them at 60' and 120' on a separate tower that just has a 75M quad at the top at 190'. So, they will be alone, more or less. The 10M ones are still being planned, but will probably be a pair on another tower, but similar in scale, etc. No interaction problems, the towers being about 150' apart.  We'll see how it goes after the alum is on the ground and how the antenna design greed goes later... :-)   The bull work is today, taking down the 400 pound log from 100'... oughta be sporting.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #39 on: August 17, 2005, 03:52:41 PM »

Tom:

I turly have forgotten how they were constructed.  But it seems as if copper tape is attached to fiberglass poles that collapse is the contruction. 

I found their website and here is how they describe the antenna, which is different from the one I saw.



 Each antenna element consists of two spools of copper strip conductor mounted in the antenna housing. The copper strips are perforated to allow a stepper motor to drive them simultaneously with a sprocket.

Stepper motors are well known for their ability to index very accurately, thus giving very precise control of the antenna length.
In addition, the motors are brushless and provide extremely long service life.

The copper strip is driven out into hollow, lightweight fiberglass support elements, forming an element of any desired length up to 36’ long. The fiberglass poles are telescoping, lightweight and very durable. When fully collapsed, each element measures 53” in length.

The ability to completely retract the copper antenna elements, coupled with the collapsible fiberglass poles makes the entire system extremely portable. The antenna is easy to assemble, and can be installed on the ground or up on the antenna tower using our Boomslide™ assembly system.





I still wonder about the copper oxidizing over time at connections points.  My Mosley beam uses copper/bronze lockwashers between the driven elements and the phasing tubes.  I have had the beam up in dry as well as high humid locations and when I put it up here, I didn't check those little lock washers.  The antenna, because the lockwashers have oxidized, now is out of tune.  I also wonder how long term the operation of the little motors will be.

I am trying to locate some stainless steel washers to replace them.  In the area I live in, they bearly know what Zinc/Steel is.  I keep joking about this part of OK, but it is true.

Jim
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« Reply #40 on: August 17, 2005, 09:58:55 PM »

Hmmm... from the description I can't figure out if the fiberglass tubes actually move for freq changes or arte fixed. Maybe they are talking about disassembly for shipping, etc.

I would rather they used FIXED hollow tubes and let the metal tape move inside. No reason to have moving mechanical tubes to fail.  The solidary moving tape sounds like an easier solution to me.

One thing I've wondered about is how vunerable are the motors to lightning?  I've lost a number of relay coils out on the tower even when lightning struck far away. Maybe they have it covered using MOVs or something.

Let me know if ya hear anything concerning  crap outs.. Seems to be a great product so far, though. 

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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