IMAX2000 no GPK vs 1/2 wave Silver Rod

[222DBFL]

Yes. Where I park Marconi is near the shore. It's a hot spot If that is what you call it. On black top pavement. It is a great spot as I am open in all directions with hardly anything around but a few palm trees.

 

[Marconi]

Here is a wider view of where this hot spot is on Galveston. The map should be active and you can make it zoom. If you zoom out to include Houston my station is right inside the Loop 610 at 290 and you can see how I am positioned relative to the Island and the sky line of downtown Houston.

https://www.google.com/maps/place/G...2!3m1!1s0x863f59c8c4059259:0xe58b03c9b9eaecc1

 

[RadioDaze2.0]

I even learnt something about Texan geography there ; )

One day when skip seems ok and the wind is low I must go out with the set up to some coastal location.

 

[Needle Bender]

Just running a few thoughts through my mind here about which antenna is the best performer for short DX sessions of a few hours when I do not have time to put an elaborate set up together. The obvious issue for my own situation is the Silver Rod is significantly shorter (18feet) and lighter meaning less hassle to erect for a static mobile station. However if I was to achieve "significantly better performance" and we can read that as a lower angle of radiation or 1dB gain approx then I would make efforts to use the IMAX2000 (24 feet and heavy) despite being heavier and longer.

Both of these antennas are ok for lower height from ground mounting on poles where the Gain Master does not fair as well typically. The GM needs to really be 1/2 wave above ground before it seems to work well.

I think if I am correct as theory would dictate these 2 antennas both without any ground plane attached should be about the same gain. We always hear the 5/8th wave has a little gain over the 1/2 wave but unless set up in perfect conditions with symetrical 1/4 wave ground planes up and away from the ground and other objects it is rarely realized over average soil.

Does this reasoning seem correct?

As an aside the IMAX never presents a VSWR lower than 1.5:1 in fact more commonly 1.7:1

I am not really happy about that and wonder if I need to in fact trim the antenna for 27.5 operation. Those tuning rings seem to be ineffectual. They may as well not be there !

Any thoughts would be appreciated.

It often comes down to an IMAX2K at 3M or a Silver Rod at 4.5M and I tend at the moment to favour the Silver Rod as the SWR is lower and I can generally get it higher. Does this reasoning seem to parallel theory regarding performance of these 2 antennas ?

Well I guess I'll add my $.00002 worth...

I bought a Proton99 just for this type of installation and was a little disappointed by it's seriously 'light-duty' construction, however, it almost kept up with my Imax 60' in a tree when mounted on a 1/2 wave high portable mast. It also stomped my A99 in several different distance tests and made me a believer.

The Good:
1) Near Imax 2000 level performance, a true 1/2 wave, 18' long above the 1' bottom mounting tube.
2) Breaks down into four 4.75' sections, 19' total versus the 17.5' A99.
3) Light and easy to quickly assemble.
4) Rated at 10 million watts - wait, ...oh yeah, 2000 watts.
5) Crazy inexpensive; $68 to my door.

The Bad:
1) Rather flimsy construction, requiring a fiberglass 'touch-up' to make it as stout as I like.
2) uhmmm...

The Ugly:
1) When assembled it's typically a little snake-ish, not straight as an arrow.
2) Needs (NON-metallic!) paint, bright white & stands out like a horse peni...

 

[M0GVZ]

The Bad:
1) Rather flimsy construction, requiring a fiberglass 'touch-up' to make it as stout as I l

That is actually a plus point. The more rigid it is the more stress it puts on the base when its windy. By "beefing it up" you may unintentionally be hastening its demise due to the additional lateral stress being placed on the base. There are times where being rigid is good and there are times where having a bit of flex is better. The reason the top section of the Imax 2000 is so bendy is it seriously reduces lateral loading on the base section when its really windy.

 

[Needle Bender]

That is actually a plus point. The more rigid it is the more stress it puts on the base when its windy. By "beefing it up" you may unintentionally be hastening its demise due to the additional lateral stress being placed on the base. There are times where being rigid is good and there are times where having a bit of flex is better. The reason the top section of the Imax 2000 is so bendy is it seriously reduces lateral loading on the base section when its really windy.

Well, actually the base is what I had to glass up, the glue used to secure the fiberglass to the metal wasn't holding & preventing from spinning, though it stayed together I felt it should have a better secured bottom section.
I also modded the top by using a Wilson whip & a 3/8 x 24 tip from a Whiskey Still type mobile antenna to cut down on the wind loading for portable application.
I set the rings to near X=0 with the original top then swap out and re-tune by trimming the whip length.

 

[Needle Bender]

Current maxima of none loaded antennas is always 1/4wave down from the tip,
The extra gain of a 5/8 over 1/2 wave is due to the tip & consequently current maxima been higher above ground,

It is also easier to make low loss matching setups for 5/8waves, nobody that I have seen makes a 1/2wave end-fed with a low loss matching setup,

A 1/2wave with an equal loss matching setup placed at the same tip height as a 5/8wave produces a little more low angle gain than a 5/8wave, The 5/8 magic disappears,

There is nothing special about a 5/8wave with its 1/8wave of out of phase radiation in the lower part of the antenna.
Its just the longest you can stretch a single element without the out of phase radiation in the lower portion spoiling the low angle radiation pattern,

Its what marconi has been telling us for years,
There should be very little to no detectable difference between the silver rod & imax when both are mounted at the same tip height unless one of them is faulty.

So Bob85, sorry, a little off-topic but I'm wondering if you've ever tried your I-10K at .64WL? I know it's only 6.5" longer but Marconi's EZNEC plots show considerable improvement at a mid angle TOA and what a mess that so-called 'small difference' makes of the SWR if the match remains adjusted for .625.
Just wondering, since I did see an improvement when tried with my I-10K several years ago and thought it might be interesting to hear your report.

 

[bob85]

No NB,
My 10k is set very close to jay's settings from the paperwork for the frequency i use,

at those settings it has a small edge on the gainmaster but its behind any of my sigma/vector antennas on the same pole,
mainly due to their extra length and height of current maxima.

 

[Crazy_D]

I have owned the Imax 2000 and the Ham International Silver Rod 1/2 wave antenna for over 20 years now. I have both antennas here broken down looking at me in the corner. I remember when I had the silver rod up (at 20ft) for a quick setup, a distant signal was giving me around a S7, when I swapped out to the imax (no gpk) the signal went up to around a S9. I got out much better with the imax in my field comparisons. When I swapped out my imax 2000 (with GPK) to a Mr coily enforcer with 7/16" din the signals went up another 1 1/2 sunits or so (on a galaxy 55/66/99 style of 60db meter), very noticeable with reduced background noise. it was like i had a amp turned on all the time when I was only running barefoot. Short 75 foot run of heliax 7/8", nothing less...

 

[Needle Bender]

I have owned the Imax 2000 and the Ham International Silver Rod 1/2 wave antenna for over 20 years now. I have both antennas here broken down looking at me in the corner. I remember when I had the silver rod up (at 20ft) for a quick setup, a distant signal was giving me around a S7, when I swapped out to the imax (no gpk) the signal went up to around a S9. I got out much better with the imax in my field comparisons. When I swapped out my imax 2000 (with GPK) to a Mr coily enforcer with 7/16" din the signals went up another 1 1/2 sunits or so (on a galaxy 55/66/99 style of 60db meter), very noticeable with reduced background noise. it was like i had a amp turned on all the time when I was only running barefoot. Short 75 foot run of heliax 7/8", nothing less...

Yepperz, that's right about what I've seen. a basic .625 = about 1 solid S-unit over an Imax2k and the .64 about .5-1 S-unit above that.
Then there's the NV4K... Still awaiting that perfect weather/energy day to replace the P500.

 

[RadioDaze2.0]

I have owned the Imax 2000 and the Ham International Silver Rod 1/2 wave antenna for over 20 years now. I have both antennas here broken down looking at me in the corner. I remember when I had the silver rod up (at 20ft) for a quick setup, a distant signal was giving me around a S7, when I swapped out to the imax (no gpk) the signal went up to around a S9. I got out much better with the imax in my field comparisons. When I swapped out my imax 2000 (with GPK) to a Mr coily enforcer with 7/16" din the signals went up another 1 1/2 sunits or so (on a galaxy 55/66/99 style of 60db meter), very noticeable with reduced background noise. it was like i had a amp turned on all the time when I was only running barefoot. Short 75 foot run of heliax 7/8", nothing less...

That is an approximate 21dB difference, that is a lot.

 

[Crazy_D]

That is an approximate 21dB difference, that is a lot.

I have done so many back and forth comparisons with all these antennas and which analyzers over the past 10-20 years, its nuts. I have spent so much time and money and effort. After I put up the coily ground plane, I change out the lmr400 to heliax 7/8 and that was also another noticeable jump in rx/tx improvement as the total losses was significantly lower. That setup outperformed a vertical 4 element maco 104 and a gizmotchy 4 element mounted at the same height by a wide margin, the only thing the beams give me was rejection, however I should note it was not a fair comparison because the beams where using lmr400 and not heliax, which is a great difference between the two, and the coily uses a superior connector (7/16" din versus so-239 on other antennas). I would have to say you would need about a 6 element maco 106 or a 5 element optimized longer boom beam to outperform that very low loss .64 groundplane heliax setup. If I ever run another coily groundplane setup in the future I am going to run the newer excalibur .64 with heliax Direct Feed connect with LDF7-50A 1 5/8" heliax.

 

[Needle Bender]

6dB per S-unit is more myth than real world. I usually figure about 1.5 to 3dB on most CBs, 3-5dB from most Amateur radios.
- Here's a good read about measured dB per S-unit: http://www.ac6v.com/sunit.htm

 

[wavrider]

6dB per S-unit is more myth than real world. I usually figure about 1.5 to 3dB on most CBs, 3-5dB from most Amateur radios.
- Here's a good read about measured dB per S-unit: http://www.ac6v.com/sunit.htm

NB I agree on the S-unit myth especially in CB's.

I do a lot of testing and experimental building on 11 meters mainly due to the fact it is not such a big antenna, cost effective, and there is always someone to get a signal report, ( helps if you know who is doing the signal report and since I align most of the radios in this area I know how many s-units per db their meter displays)
Usually about 3 db per S unit on most rigs until you get to S9 then it is anyone's guess.

 

[wavrider]

I have done so many back and forth comparisons with all these antennas and which analyzers over the past 10-20 years, its nuts. I have spent so much time and money and effort. After I put up the coily ground plane, I change out the lmr400 to heliax 7/8 and that was also another noticeable jump in rx/tx improvement as the total losses was significantly lower. That setup outperformed a vertical 4 element maco 104 and a gizmotchy 4 element mounted at the same height by a wide margin, the only thing the beams give me was rejection, however I should note it was not a fair comparison because the beams where using lmr400 and not heliax, which is a great difference between the two, and the coily uses a superior connector (7/16" din versus so-239 on other antennas). I would have to say you would need about a 6 element maco 106 or a 5 element optimized longer boom beam to outperform that very low loss .64 groundplane heliax setup. If I ever run another coily groundplane setup in the future I am going to run the newer excalibur .64 with heliax Direct Feed connect with LDF7-50A 1 5/8" heliax.

Crazy D. with all due respect, I have 35 years in communications and I have never seen any transmission line, be it ladder line, coax, hard line, or even fiber optic than can INCREASE SIGNAL strength of an RF signal.

The claims of your heliax greatly improving tx and rx over lmr400 at HF frequency would need to have some very expensive, sensitive test equipment to see any difference in receive or transmit.

A simple S meter on a CB would not even show a needle width of difference.

Post a video or something to substantiate your claim.

Not saying you are not telling the truth, just looking at specifications of cable loss at HF freq for the two transmission cables you are using.

Now if it was UHF MAYBE there could be that big a difference.