tag:blogger.com,1999:blog-4901205574058136834.post3239548641959062560..comments2024-03-26T20:17:30.126-07:00Comments on Every Blade of Grass: Antenna Workdrjimhttp://www.blogger.com/profile/05647484115197408897noreply@blogger.comBlogger11125tag:blogger.com,1999:blog-4901205574058136834.post-20055982451423682692016-01-17T20:25:55.871-08:002016-01-17T20:25:55.871-08:00Of course it does, but I've run the radio hori...Of course it does, but I've run the radio horizon profiles using SPLAT!, and they're not 30dB different, which is about what it seems like.<br /><br />I'm starting to suspect the coax may have gone south. It's 20 years old, and *looks* to be in great shape, but I'm just gonna have to run the loss measurements on it.<br /><br />It has a polyethylene outer jacket, and it's rated for direct burial, so being gently handled (no kinks or 'too tight' bends) and just laying on the roof for the last 20 years shouldn't have degraded it excessively....drjimhttps://www.blogger.com/profile/05647484115197408897noreply@blogger.comtag:blogger.com,1999:blog-4901205574058136834.post-60615420432554267602016-01-17T19:25:18.034-08:002016-01-17T19:25:18.034-08:00Altitude plays into it. You were thirty feet up at...Altitude plays into it. You were thirty feet up at the apartment, now you're 15 feet up... Do your horizon calcs and I'll bet you find that is the difference.Old NFOhttps://www.blogger.com/profile/16404197287935017147noreply@blogger.comtag:blogger.com,1999:blog-4901205574058136834.post-11340271163175108162016-01-17T13:24:36.830-08:002016-01-17T13:24:36.830-08:00SiG, I frankly don't know. From reciprocity, y...SiG, I frankly don't know. From reciprocity, you'd sure think that degraded receive would show up in degraded transmit, and on the VSWR plots.<br /><br />I'm just about to make some measurements and then go "fix" the problem.<br /><br />If I can figure out how to post a pdf, I'll post the before and after plots. I might have to convert them to jpg or png so Blogger will accept them.<br /><br />Stand by for a new post in a couple of hours.....drjimhttps://www.blogger.com/profile/05647484115197408897noreply@blogger.comtag:blogger.com,1999:blog-4901205574058136834.post-22237366589699015152016-01-17T13:21:39.985-08:002016-01-17T13:21:39.985-08:00Yep, Diamond and Comet antennas look, act, and &qu...Yep, Diamond and Comet antennas look, act, and "feel" almost the same.<br /><br />The only difference I've found is Diamond antennas cost a few $$ more!drjimhttps://www.blogger.com/profile/05647484115197408897noreply@blogger.comtag:blogger.com,1999:blog-4901205574058136834.post-91462182930170881472016-01-17T13:03:50.762-08:002016-01-17T13:03:50.762-08:00The "works well on transmit but not receive&q...The "works well on transmit but not receive" thing makes me think you have some losses there that aren't obvious. Antennas are pretty reciprocal in behavior. Like you say, the transmit load ought to be a good indicator. So the question is what makes transmit look good but receive worse? <br /><br />If you're doing a low band vertical, you really don't want 50 ohms; ideal is closer to 35. You can put down radials for a 1/4 wave vertical and make the VSWR worse. If you're seeing 50 ohms with only a few or no radials, the transmitter VSWR looks good but doesn't perform well in terms of getting power out. It may be more noticeable on receive. <br /><br />Something like that?<br /><br />SiGraybeardhttps://www.blogger.com/profile/00280583031339062059noreply@blogger.comtag:blogger.com,1999:blog-4901205574058136834.post-15676128771626658822016-01-17T13:02:32.189-08:002016-01-17T13:02:32.189-08:00http://www.diamondantenna.net/x50a.html
http://www.diamondantenna.net/x50a.html<br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4901205574058136834.post-26972687152570351582016-01-17T13:01:06.135-08:002016-01-17T13:01:06.135-08:00That antenna looks exactly the same as the Diamond...That antenna looks exactly the same as the Diamond X-50A. I think they are the same, just different names, both Japanese. I have an old hand me down Diamond I haven't used yet. <br />Terry<br />Fla.Terryhttp://jterryt.blogspot.comnoreply@blogger.comtag:blogger.com,1999:blog-4901205574058136834.post-1131069752840314312016-01-17T11:27:58.997-08:002016-01-17T11:27:58.997-08:00I think it's a bit "short" to make m...I think it's a bit "short" to make much difference, but I may very well be proved wrong.<br /><br />The thing is, the VSWR from my plots matches the published curves. If a significant chunk of the counterpoise was missing, I'd expect the VSWR to be high....drjimhttps://www.blogger.com/profile/05647484115197408897noreply@blogger.comtag:blogger.com,1999:blog-4901205574058136834.post-56979819381093993022016-01-17T11:18:22.810-08:002016-01-17T11:18:22.810-08:00245mm? Hmmm. That's around 9 1/2 inches, whi...245mm? Hmmm. That's around 9 1/2 inches, which is about an eighth wave on 2m. That's certainly "electrically significant". Is that some sort of counterpoise that helps tune the antenna? <br />SiGraybeardhttps://www.blogger.com/profile/00280583031339062059noreply@blogger.comtag:blogger.com,1999:blog-4901205574058136834.post-89669193547641422382016-01-16T21:32:03.673-08:002016-01-16T21:32:03.673-08:00I'm not that good.....
It worked fine before,...I'm not <i>that</i> good.....<br /><br />It worked fine before, so I just have to go back to the original configuration.<br /><br />I'll make a few before/after measurements to see if anything looks different.drjimhttps://www.blogger.com/profile/05647484115197408897noreply@blogger.comtag:blogger.com,1999:blog-4901205574058136834.post-14176985897785200592016-01-16T20:43:08.359-08:002016-01-16T20:43:08.359-08:00If YOU can't make it work, nobody can.If YOU can't make it work, nobody can.LLhttps://www.blogger.com/profile/05538854359365988863noreply@blogger.com