This morning I helped out Jim, N1WWE, check out his Cushcraft R7000 vertical prior to final installation. This is a 40 -10 antenna that mounts on a mast. The directions (TNX de K1DM) says if not mounted on a tower or structure, a 10 foot mast on the ground will do. Well, prior to permanent installation on a mast in his back yard, I checked all the dimensions and propped it up against his deck to check the SWR on each band with my MFJ analyzer. Some of the dimensions were “off” from those given in the instrctions by about an inch…but the top section was over a foot longer than indicated in the instructions. After making the lengths correct, what were the results?
Horrible! It was pretty flat at about 2:1 across 10 meters…just as the directions say. 12 meters the best point was about 2.6:1. But there was no resonant point anywhere near 17 meters….15 and 20 meters were not much better…and 40 meters was resonant (that is around 2: 1 at best) below the band. I didn’t even attempt to tweak the antenna adjustments since there was really no place to even start on 17, 15, and 20 meters.
This seemed to coincide with the reviews on eHam that for the most part concluded that this antenna is CRAP!!. Some indicated that when you tweak it on one band, it then srews up the other bands. Based on the comments, s-canning this antenna seemed to be the preferred route. Could this antenna be really that bad? Or could it really make that much of a difference by getting it up in the air and off the ground?
Jim seemed to remember that when originally set up some time ago at a previous location, that Cushcratf had sent him some addendum of instructions as there was a change made in its configuration….maybe the directions I have are for a different earlier (or later) version?
Jim’s previous antenna at this location (before Sandy) was a coax fed 135 foot dipole that with a tuner he used successfully on all bands. It goes from the peak of the house (about 40 feet) to a flagpole. It seems that we will re-do this antenna with new wire and coax …and leave the R7000 on the garage floor.
Anyone have any thoughts or experience with the R7000 that would explain the results we got?
— John, W1XX
John,
If you go to http://www.cushcraftamateur.com/prodsupport.php you will find two separate manuals for the R7000 (without 80M add-on kit). I don’t know which one you are using but there is one from 10/96 and one from 7/99. Some dimensions are significantly different from each other, specifically, dimensions B and C, which affect 30M, 20M, 15M, and 17M. Perhaps this will help.
73,
Pat, NG1G
I should also have mentioned that per the instructions, it’s critical that you adjust the antenna from the bottom to the top (as you have seen from the reviews). If I recall, this is how my R5 works as well. These verticals work best when “in the clear” but not necessarily way above ground.
As for the reviews…my guess is those people who assembled their R7000 and couldn’t get it to work probably never actually read the manual and instead just slapped it together. I’d try it with the “latest” dimensions (if you haven’t already), put it as far away from obstructions as possible, and see what happens.
73,
Pat, NG1G
TNX, Pat. The instructions used were from 96 when the antenna was purchased. That should be correct. But maybe CC found out over time from the many complaints, that the dimension settings were not correct and published the 99 figures which are significantly different from the 96 figures. So we are going to try it again tomorrow with the 99 dimensions and see if it tunes properly. Yes, I knowe you tune from the bottom. I think the reviewers were not all lids…there are just too many nay-sayers. It does appear clear that the coils cannot handle a KW …but N1WWE has never run power so this is not an issue. He has a pacemaker! It will not be totally in the clear however, as the “stealth” nature of the installatioon requires it be somewhat close to some trees/bushes at least on one side. Maybe we can get it somemwhat more in the clear than origianlly intended. We’ll see what happens in Test #2. Again, TNX! 73! — John, w1XX
I don’t want to leave the impressaion that this antenna is a complete loser. Armed with an updated set of instructions…I went back over to N1WWE’s house and re-checked the antenna. To my surprise, I discovered it had been put together totally wrong…the coils were upside down (shudda noticed this before). It seems that when Jim moved … the antenna was “thrown together” to aid in the moving…incorrectly. After 3 trials to get the SWR in range on each band, the antenna looks FB for use. Next step is to install it on an EMT 10 foot pipe as suggested by K1SD (I think). Out!
John,
Sounds like you are making progress. Pat is correct. There were a couple versions of the instructions that I sent you. I sent only one. Coils mounted upside down with these vertical (or Tribanders) can cause problems. I anticipate that things will change when you get it away from close-by structured – like dirt, wood, etc. Metal will definitely make a difference.
Always remember – Antennas are black magic! 73, K1DM, Dr. Mike