Re: Topband: Newbie Antenna Question (long)
Having a strong high angle lobe can be a benefit when seperate receiving antennas are used. It keeps locals further away and is a favorite trick of contesters on all bands. With yagis just feed a small portion to a low antenna pointing backwards from the direction being worked. Ive repeatedly mentioned on here that there are many times where a high angle works best for 160M DX and throwing it away may not be a good idea. It might also be geographically dependent. OTOH modeling has shown that the 1/4 wave Inverted L I had installed for 600M at 160' vertical and 300' sloping to 60' could be improved by 1dB going to a 2 wire tophat. It hasnt been detemined if the missing high angle will be detrimental. Carl KM1H - Original Message - From: "Jim Brown" To: Sent: Tuesday, September 06, 2011 12:47 PM Subject: Re: Topband: Newbie Antenna Question (long) > On 9/5/2011 8:03 PM, Jim Bennett wrote: >> The ARRL Antenna Book, and ON4UN's Low Band DX'ing book, I accept the >> fact that a vertical antenna is the best bet (for transmitting, anyway) >> 160 meters, AND that the Inverted L is basically a vertical antenna. If >> that is the case, does this mean that it radiates just like any other >> vertical, primarily omnidirectional? If it is omnidirectional, does it >> matter in which direction the horizontal portion of an Inverted L is >> aimed? > > The vertical wire is omni and radiates at a low angle, the horizontal > wire serves to resonate it and radiates at a high angle (for local > contacts). A Tee top to the vertical (rather than the L) provides the > same top-loading to resonate the wire, but the radiation from the top > section cancels itself out so that only the bottom section is working. > Thus, a Tee is a better low-angle antenna. > > The K6MM vertical is a compromise for when you can't string something > into a tree. The wire in the tree is likely to work a lot better. With > either, do the best you can with radials and have fun. > > It's worth trying to make that vertical as tall as practical, given your > limitations. Taller means a higher radiation resistance, which means > less loss in your radial system. > > 73, Jim K9YC > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > - > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1392 / Virus Database: 1520/3881 - Release Date: 09/06/11 > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Newbie Antenna Question (long)
On 9/5/2011 8:03 PM, Jim Bennett wrote: > The ARRL Antenna Book, and ON4UN's Low Band DX'ing book, I accept the fact > that a vertical antenna is the best bet (for transmitting, anyway) 160 > meters, AND that the Inverted L is basically a vertical antenna. If that is > the case, does this mean that it radiates just like any other vertical, > primarily omnidirectional? If it is omnidirectional, does it matter in which > direction the horizontal portion of an Inverted L is aimed? The vertical wire is omni and radiates at a low angle, the horizontal wire serves to resonate it and radiates at a high angle (for local contacts). A Tee top to the vertical (rather than the L) provides the same top-loading to resonate the wire, but the radiation from the top section cancels itself out so that only the bottom section is working. Thus, a Tee is a better low-angle antenna. The K6MM vertical is a compromise for when you can't string something into a tree. The wire in the tree is likely to work a lot better. With either, do the best you can with radials and have fun. It's worth trying to make that vertical as tall as practical, given your limitations. Taller means a higher radiation resistance, which means less loss in your radial system. 73, Jim K9YC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Newbie Antenna Question (long)
On 09/05/2011 11:03 PM, Jim Bennett wrote: > I accept the fact that a vertical antenna is the best bet (for transmitting, > anyway) 160 meters, AND that the Inverted L is basically a vertical antenna. > If that is the case, does this mean that it radiates just like any other > vertical, primarily omnidirectional? If it is omnidirectional, does it matter > in which direction the horizontal portion of an Inverted L is aimed? I can > run mine in either of two different directions; one higher, but not too > stealthy, the other direction a tad lower, but more hidden from the HOA Nazis. > > Oh, and yes, I am planning on installing several long radials. It would > be great if I could plop down 50-100 of 'em, but that isn't realistic, > either! I've already got two strung out along the fence perimeter, and I > might be able to get one or two more put down, providing the XYL doesn't go > ballistic with all the wire strung out around the house. At least she's also > a ham, so she "might" cut me some slack on that part of the project! The double L antenna could be a stealthy alternative too, which does not require radials. It outperforms an inverted L with a smaller number of radials and comes pretty close to the performance of an inverted L with a reasonable number of radials. Depending on how much copper you want to sink into the ground (60+ radials could be a lot of work and I don't know how much time/energy you have), it could go either way. Here is some info on the double L antenna: http://www.yccc.org/Articles/double_l.htm http://surriel.com/radio/160-meter-double-l-antenna As you can see from the photos, it's barely visible. The performance is 6dB (1 S point) below a vertical over perfect ground. That corresponds to maybe 2-3dB below that of an inverted L with 30-70 1/4 wave radials over poor ground. Given that I do not have the space for that many 1/4 wave radials on 160m, I'll take the low effort antenna any day over 2dB more performance for 10x as much work :) You can add radials over time to get some more performance, but the double L does not require them to get started... -- All rights reversed. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Newbie Antenna Question (long)
Hi folks - I'm new to this list and fairly new to 160 meters and I've got a couple questions. I've been licensed since '64 and have spent the majority of my hamming on CW, 80-10 meters. A couple years ago I built a "shortened, half sloper" for 160 meters. It worked "OK", but certainly wasn't the kind of antenna one will get DXCC on 160 with. I made perhaps 50-100 QSOs with it doing occasional operating on 160, and none any further than Texas. But I digress... I recently moved to this QTH (Folsom, CA) and have a very nice, 21 year old home that, unfortunately, came with CC&R and HOA. Not a huge deal, as the HOA really has no teeth. But just the same, I don't want to be bombarded with nasty notes from the HOA, so I've tried to go "stealthy" with my antennas. I was able to put up an 88 ft long doublet, hidden in the trees, fed with 80 ft of 600-ohm ladder line. It works very, very well on every band from 80 through 6 meters. Alas, the tuner in my Elecraft K3 isn't up to the task of making this doublet work on 160. And, I do want to get up some sort of antenna to at least make a lot of stateside QSOs. DX would be nice, but being realistic, I'll probably not be able to erect much of a competitive, DX-worthy antenna on this property. We have several 50 ft high redwood trees across the back of the property, and another one right out by the street in front. One side of the house is lined with some 40 ft high liquid amber trees, and one of them serves as the support for one end of my 80-6 doublet. I ran across an article by K6MM about a helically-wound, 30 ft tall vertical for 160 meters. I was going to build one and give it a try when another fellow mentioned that I ought to first try putting up an Inverted L antenna, given that I have a bunch of redwoods on the property. So, I'm about half way into the Inverted L project and had a couple questions. I got the vertical part of the antenna installed this afternoon. The best I could do was to get it straight up to a height of 35 ft. Now I'm ready to feed out the remainder of the wire in the horizontal plane. After reading (and attempting to comprehend!) the ARRL Handbook, The ARRL Antenna Book, and ON4UN's Low Band DX'ing book, I accept the fact that a vertica l antenna is the best bet (for transmitting, anyway) 160 meters, AND that the Inverted L is basically a vertical antenna. If that is the case, does this mean that it radiates just like any other vertical, primarily omnidirectional? If it is omnidirectional, does it matter in which direction the horizontal portion of an Inverted L is aimed? I can run mine in either of two different directions; one higher, but not too stealthy, the other direction a tad lower, but more hidden from the HOA Nazis. Oh, and yes, I am planning on installing several long radials. It would be great if I could plop down 50-100 of 'em, but that isn't realistic, either! I've already got two strung out along the fence perimeter, and I might be able to get one or two more put down, providing the XYL doesn't go ballistic with all the wire strung out around the house. At least she's also a ham, so she "might" cut me some slack on that part of the project! I do have a licensed copy of EZNEC and I've downloaded the free cocoaNEC program for Mac (provided by W7AY). Unfortunately, I just don't seem to be able to get my brain working properly to use either of these programs to model this Inverted L. I suppose if I were proficient with either one, this posting would not be happening! So, can anyone enlighten me on the subject of that horizontal wire component of the Inverted L antenna? Thanks, Jim / W6JHB ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
