Re: Topband: NVIS Antenna
Receive only comment. A low dipole - 15 feet average, uneven ground - Receive Only - accounted for something like 40% of the contacts with NA from XZ0A. During the first 2 hours at Sunset, the low dipole heard signals that the admittedly not all that good beverages could not hear at all. Site had a pretty good noise floor for Asia. on an island on Diesel power. This was during a higher portion of the sunspot cycle so the polar oval was quite large preventing most of NA from having a clean direct path. Our signal - 1500W into a elevated radial elevated feedpoint full size quarter wave tower - was invariably heard via the SW path when heard east of the Midwest. so we were dealing with ducting and greyline bending. the point is - again - you can never have too many receive antennas. An NVIS receive antenna can significantly benefit your receive capabilities. YMMV especially based on location. Equatorial regions seem to benefit more from NVIS RX and or Horizontal polarization. On Transmit it appears the ground absorption negates the benefits for longer haul paths where better efficiency is needed - until you get the dipole high enough to stop heating the gophers. Robin WA6CDR XZ0A-XZ1N, etc - Original Message - From: "Wes" To: Sent: Sunday, March 15, 2020 13:03 Subject: Re: Topband: NVIS Antenna When I decided on the new challenge of working DXCC on 160 for my ninth band, I added some extensions on my 80-meter inverted-vee , (apex at 45') and tied them off on some handy saguaro cacti about head high. You don't climb these :-) I worked my first 80 or so countries with it. And this is from southern AZ, not Maine. K3S + KPA500. Wes N7WS On 3/15/2020 12:47 PM, Carl Luetzelschwab wrote: For those who are antenna challenged, don't sell a 160m inverted-vee at low height too short. My 160m antenna at the moment is an inverted-vee at an apex of 45 feet. Additionally, the last third of each end is at 90 degrees to the main portion and horizontal at only 7 feet or so off the ground. It's what fits on the property. In the CQ 160m CW contest in January 2017. I came away with 44 states (missed ME, ID, NE and AK), 7 Canadian provinces (VE9, VY2, VE2, VE3, VE5, VE6 and VE7) and 17 DXCC entities (mostly Caribbean, Central America, Mexico and South America, with a few Europeans, a North African and a KH6 in the mix). I was seldom #1 in a pile-up, but eventually I usually got through with 800 Watts to the inv-vee. It's better than no antenna. Carl K9LA _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Stew Perry Preliminary Results posted
Great to see so much activity for the Spring Stew. Was sorry to miss it myself. The preliminary results are now online: https://www.kkn.net/stew/stew_results.html 73 Tree N6TR _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: NVIS Antenna
When I decided on the new challenge of working DXCC on 160 for my ninth band, I added some extensions on my 80-meter inverted-vee , (apex at 45') and tied them off on some handy saguaro cacti about head high. You don't climb these :-) I worked my first 80 or so countries with it. And this is from southern AZ, not Maine. K3S + KPA500. Wes N7WS On 3/15/2020 12:47 PM, Carl Luetzelschwab wrote: For those who are antenna challenged, don't sell a 160m inverted-vee at low height too short. My 160m antenna at the moment is an inverted-vee at an apex of 45 feet. Additionally, the last third of each end is at 90 degrees to the main portion and horizontal at only 7 feet or so off the ground. It's what fits on the property. In the CQ 160m CW contest in January 2017. I came away with 44 states (missed ME, ID, NE and AK), 7 Canadian provinces (VE9, VY2, VE2, VE3, VE5, VE6 and VE7) and 17 DXCC entities (mostly Caribbean, Central America, Mexico and South America, with a few Europeans, a North African and a KH6 in the mix). I was seldom #1 in a pile-up, but eventually I usually got through with 800 Watts to the inv-vee. It's better than no antenna. Carl K9LA _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: NVIS Antenna
For those who are antenna challenged, don't sell a 160m inverted-vee at low height too short. My 160m antenna at the moment is an inverted-vee at an apex of 45 feet. Additionally, the last third of each end is at 90 degrees to the main portion and horizontal at only 7 feet or so off the ground. It's what fits on the property. In the CQ 160m CW contest in January 2017. I came away with 44 states (missed ME, ID, NE and AK), 7 Canadian provinces (VE9, VY2, VE2, VE3, VE5, VE6 and VE7) and 17 DXCC entities (mostly Caribbean, Central America, Mexico and South America, with a few Europeans, a North African and a KH6 in the mix). I was seldom #1 in a pile-up, but eventually I usually got through with 800 Watts to the inv-vee. It's better than no antenna. Carl K9LA _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: NVIS Antenna
Inverted vee dipoles do produce some vertically polarized radiation off the ends. However, that vertical component has maximum gain at zenith, i.e. straight overhead. It does not contribute to any significant low-angle radiation. You can see this by doing an antenna model. 73, John W1FV -Original Message- From: Topband [mailto:topband-bounces+john.kaufmann=verizon@contesting.com] On Behalf Of Jim Brown Sent: Sunday, March 15, 2020 2:36 PM To: topband@contesting.com Subject: Re: Topband: NVIS Antenna Hi Ed, I've studied this extensively for horizontally polarized antennas, but only for flat ones; I thin that inverted Vees have some vertical components. For horizontally polarized antennas, maximum gain at high angles occurs at a mounting height of about 75 electrical degrees, and falls by only about 1 dB if raised to 120 electrical degrees. By "high," I'm talking 70 degrees elevation. Also, RX is different from TX, in that with RX we don't care about loss, only signal to noise. Ground loss is a contributor to those variations based on mounting height. N6RO, an old hand on topband with a great antenna farm, rearranges his M/6 station for topband contests to bring LOTS of his antennas to the station he uses single-op. That study is here. http://k9yc.com/AntennaPlanning.pdf 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: NVIS Antenna
Hi Ed, I've studied this extensively for horizontally polarized antennas, but only for flat ones; I thin that inverted Vees have some vertical components. For horizontally polarized antennas, maximum gain at high angles occurs at a mounting height of about 75 electrical degrees, and falls by only about 1 dB if raised to 120 electrical degrees. By "high," I'm talking 70 degrees elevation. Also, RX is different from TX, in that with RX we don't care about loss, only signal to noise. Ground loss is a contributor to those variations based on mounting height. N6RO, an old hand on topband with a great antenna farm, rearranges his M/6 station for topband contests to bring LOTS of his antennas to the station he uses single-op. That study is here. http://k9yc.com/AntennaPlanning.pdf 73, Jim K9YC On 3/15/2020 9:28 AM, sawye...@earthlink.net wrote: I put up a 160M full size inverted vee. Top at about 55ft and ends at around 15 feet. Just high enough to decouple some of the ground losses but other than that, straight up radiation for the most part. _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: NVIS Antenna
I was reminded of my interest in re-installing a low 160M antenna to supplement by 2 el vertical phased array. And since there was no where to go this weekend and no College Hoops to watch, I thought, hey, I could get something up and play around with it in the Spring Stew. And that what I did. I put up a 160M full size inverted vee. Top at about 55ft and ends at around 15 feet. Just high enough to decouple some of the ground losses but other than that, straight up radiation for the most part. I compared that to my 2 element T top vertical phased array that is half wave spaced and fed in phase or 180 out of phase for an E/W or N/S pattern. At about 2 hours before sunset I started tuning around and listening to stations. Understand from my location in Vermont there is literally no one on within 100 miles of me almost all the time. Unless W1SJ or K2LE are on (SJ is 40 miles and LE is 80 miles). I was interested to hear that until about 30 mins before sunset - NONE of the signals we better on the NVIS inv vee - in fact virtually all were down by 5 - 15db. Then around that time I started to notice that the 200 mile out stations and as well the closer stations started being equal on the NVIS and a few louder by maybe 5dB. Then from Sunset for a good hour or more, MOST of the up to 200 mile out stations were 5 - 15dB louder on the NVIS inverted vee. Propagation is fascinating. It's a keeper to have in the arsenal for the selected need of 200 - 250 miles out from an hour before to maybe 1 - 2 hours after sunset on 160M. Comments welcome. 73 Ed N1UR _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Slightly OT - amplifier noise
A couple of issues I see. It depends which direction(s) the noise and desired signal are coming from. You may null the noise and signal. Also, the loop is bi-directional. I've been playing with a DX Engineering RF-PRO-1B at ET3AA and it works. Thanks to Tim and the gang for their support. But there is a lot of noise and not being able to null everything except the desired direction I suspect is an issue. Our noise is close in, so I have some upgrades in place using a Hi-Z 4 square and NCC-2 with a "noise" antenna as Frank mentions. Unfortunately the next thing I need to do after I send this, is to cancel my reservation for the 27th of this month. Africa looks like a pretty safe place Covid-19 wise at the moment. But one look at the long lines at immigration did me in. I don't have the patience for that. 73 Ken K4ZW On Sat, Mar 14, 2020 at 11:43 PM wrote: > > > Hi Rick, > > > > A noise receiving antenna close to a noise source is used in conjunction > with a higher performance receiving antenna such as a Beverage or an > array of short verticals and a passive or active noise canceller. > > > > A small loop antenna provides a mechanically steerable null off of both > sides of the loop. Null beamwidth is just a few degrees at the 3 dB > points, otherwise a small loop is an omni-directional receiving antenna. > Simply turn the loop to minimize the interfering noise signal strength. > > > The smaller the loop, the deeper the null depth but the smaller the signal > strength of desired signals. A small loop antenna requires a low noise > high gain pre-amp directly at its feed point for optimum sensitivity. > > > A small loop antenna should be close to ground for optimum null depth. > Horizontally polarized skywave signals penetrate the nulls if a small > 160 meter loop antenna is much higher than than about ten feet above the > ground > > > On 160 meters a small loop antenna provides: > - a 30 dB null off each side of a 5 foot diameter loop. > - a 25 dB null off each side of a 10 foot diameter loop, or > - a 20 dB null off each side of a 17 foot diameter loop > > > 73 > > Frank > W3LPL > > > > > > > > > - Original Message - > > From: "Richard (Rick) Karlquist" > To: "Dave Cuthbert" , n...@arrl.net > Cc: "Topband" > Sent: Saturday, March 14, 2020 10:17:59 PM > Subject: Re: Topband: Slightly OT - amplifier noise > > > I am trying to understand what these noise cancelling > schemes do that couldn't be done with a simple loop > (rotating the loop until the noise drops into one of > the null directions). You can easily prove to yourself > with a hand held AM BCB receiver equipped with a ferrite > bar antenna that even the worst power line noise can > almost always be greatly suppressed by properly rotating > the receiver. Similarly, I have had good luck with > small tuned loops (10 feet perimeter) nulling power > line noise. Smaller loops seem to have deeper nulls. > > It is critical to keep loops away from your other antennas > and power wiring. Otherwise, they will not exhibit a > good null. > > Rick N6RK > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
