Hi Rich,
Technically the coax is the same. It's the same brand, Intercom, and model, 2482 RG-58C/U, coax. Had about 13 feet or so rolled in a coil so I cut it and made two pieces, one for 144 the other for 440. BNC's on both ends. The only difference now is the length is a little longer, by a couple feet, for both instead of the single shorter piece supplied by Arrow.
There very well could be problems with the soldering connections on the diplexer itself or the BNC connectors. However, I'm not seeing anything that indicates a short or open anywhere on the diplexer board or connectors. However, it's still possible. I don't have an Elk antenna, just the Arrow so I'm not comparing or working with 2 different antennas.
As for additional variables, as I mentioned in the first post i was using a TH-D7A(G) HT with the Arrow. I've purchased a TM-D710 mobile rig and use it for the sats. The HT has a problem with the headphone jack, but the speaker works fine so there's no problem with the receive audio. My comparisons are using both rigs, not on the same pass obviously, with the Arrow diplexer and the Comet diplexer. Even with the HT, there is a considerable difference in what is copied compared to before.
You mention about the Elk's F/B ratio. I've noticed the same thing on the Arrow. A while back, before the new diplexer, I contacted a local about 15 miles away, he was running about 2 watts and no matter which direction I turned the beam, the signal strength never changed. Hmmm.
I wholehearted agree with you that both antennas are very well assembled. There has never been any questions about the quality of the material or workmanship of either. However, there is one thing that most people get drawn into and that is the statement you made "both antennas work pretty darn good." Just about anything will "work" if it happens to be close enough to its sweet spot. What needs to be focused on is how efficiently is it performing? Let's get it in the sweet spot. I would rather have any object, including an antenna, to not only work, but work at its best efficiency. Let me make my point using a popular antenna in today's HF communication. This is the 43 vertical antenna. Don't get me wrong, there is absolutely nothing wrong with the 43 foot vertical. The antenna performs well on the lower bands, 40, 30, 20 and 17 meters. 80 meters requires a loading coil but that's no big deal. The problem lies in the performance above 17 meters. Sure, you can make some contacts but the radiation pattern is so poor you'd wonder how you ever made the contact.
Let me make another analogy pertaining to work and working efficiently. I had a Pontiac 1996 Grand Am with a 3.1 liter V-6 engine. It put out 175 horsepower at 5200RPM with 195 F/P of torque. I now have a 2008 Toyota RAV4 with a 3.5 liter V-6 engine that put's out 269 horsepower at 5200RPM with 248 F/P torque. The kicker, the RAV4 weighs 800 pounds more and gets better gas mileage than the Grand Am. I know what everybody is thinking, "geez, there's 12 years difference between the two so the technology has changed so there should be an improvement." To a degree, your correct in thinking that. However, over that amount of time it was designed, tested, redesigned, retested, to work efficiently, not just work.
73,
Jeff WB3JFS
----- Original Message ----- From: "KI6RRQ" [email protected] To: [email protected] Sent: Saturday, October 03, 2009 2:49 PM Subject: [amsat-bb] Arrow Diplexer loss + Arrow v Elk
Jeff, you said; "The antenna and coax remain the same, the difference, the diplexer."
My Arrow diplexer has three factory fixed wires coming out of it, one for the radio and two that go to BNC connectors on the Arrow antenna. So, you cannot say; the coax remains the same! The coax on your diplexer or the connections to it, can be at fault as well. These coax wires and how well they are connected to the Arrow diplexer, are another variable that you have not considered in your statement because they are removed from the mix when using the Elk, unless you are trying to use the Arrow diplexer on the Elk Log Periodic antenna, Which I doubt because I am assuming you used the same one radio configuration on the Elk as you did the Arrow with your diplexer but if you are that could be presenting some other variables to produce the results your experiencing. You have to use different cables for your Comet Duplexer on the Arrow, from the Comet, to the antenna connection.
Although, I agree that the Arrow seems to pick up the signal a little later then my Elk antenna, both antennas work pretty darn good, IMO. I like them both and recommend them both. I do not have a technical background so my comments here, are all anecdotal in nature but the other thing I have noticed between the two antennas, is that when I make terrestrial contacts with them, the Elk appears to radiate almost as well toward the back, as toward the front. I have been told this is called front to back ratio. If I point north, a guy from the south calls back and I tell him, wow I am pointed north, let me turn and point it toward you.......any better.... And usually there is little if any improvement, while on the Elk and what blows my mind is, there is also a fair bit of response from people even 90 degrees from the business end of the Elk. I have tried the same with the Arrow and gotten much different reports. This is only a general statement; I think the Arrow has a better front to back ratio, more energy going out the front end but I know there are other variables such as; hand held or up on the tripod I use to hold them each up (at times) and perhaps the ground under me, or the moisture in the ground during the different attempts, etc. (4-5' above the ground on tripod and me not always right behind it, so plenty of variables but in general, that is my experience in the field)
Nevertheless, I have mentioned this to several on the board who have the Elk's and no one has responded that they have tested there's in this regard, so take this with a grain of salt for now. To others, I would love to hear your experience in this regard. I have asked a capable HAM friend to help me figure this out, properly, so one day I will have more then anecdotal info.
I think both antennas are very well built and work well for satellite and emergency communications! I have often pulled one of them out, with success, when band conditions would not allow an Omni to get the job done on my VX-7R. I found the Elk a little cheaper to buy unless you do not purchase the Arrow diplexer. For others I will point out that, you can use the Arrow with two radios without a duplexer, with same two radio configuration, you will need a duplexer for the Elk and of course the reverse is true if you are using one radio for dual band work, as I do, the Arrow will require a duplexer and the Elk will not. Also as many of you know the Arrow diplexer is only rated for 10 watts but without it both antennas will handle much more.
73 de Rich KI6RRQ
Message: 15 Date: Fri, 2 Oct 2009 23:26:38 -0700 From: "Jeff Yanko" [email protected] Subject: [amsat-bb] Re: Arrow antenna reconfiguration results - UPDATE To: "Gary "Joe" Mayfield" [email protected], "'Charles Suprin'" [email protected]
Could very well be.
73,
Jeff WB3JFS
----- Original Message ----- From: "Gary "Joe" Mayfield" [email protected] To: "'Jeff Yanko'" [email protected]; "'Charles Suprin'" [email protected] Subject: RE: [amsat-bb] Re: Arrow antenna reconfiguration results - UPDATE
We are missing the easy answer. He had diplexer that was off spec. It happens.
73, Joe kk0sd
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jeff Yanko Sent: Thursday, October 01, 2009 4:28 PM To: Charles Suprin Subject: [amsat-bb] Re: Arrow antenna reconfiguration results - UPDATE
Hi Charles and the group,
FB on the numbers. Interesting to say the least and thanks for taking the time to look further into this topic.
Questions? I have a few after looking at these numbers and performing more observations.
First, are you testing just the diplexer and not the diplexer and the antenna combined? This could result in an overall number and not just the diplexer alone. How could there be a large discrepency between preliminary reports, 2.65dB and .5dB now. Could be equipment calibration, human error, etc. from previously tested, or attempted testing of the device. I don't believe any improvements have been made to the Arrow diplexer, but who knows?
Second, I switched back to the Arrow diplexer and made another comparison with the Comet diplexer. Again, no comparison, the Comet outperformed. Why would this happen if the two are pretty close to one another in numbers. The Comet has .25db loss at VHF and .26 at UHF.
Third, with the Arrow diplexer I wouldn't begin to receive the birds until almost 3 minutes after AOS, with the Comet diplexer a minute to 1.5 minutes after AOS. Yes, watch calibrated to WWV and multiple times of acquiring the birds. I've tried both setups with the HT and D710 and they both show the same results respectively, Arrow diplexer vs. Comet diplexer. The antenna and coax remain the same, the difference, the diplexer. May not be test lab quality but something is proving itself. What is it?
Finally, is it just my Arrow diplexer? Doesn't appear to be shorted or any defects to it. Actually looks great and assembled very well. I've encountered others saying the same thing. However, a very noticable difference to the overall performance.
73,
Jeff WB3JFS
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