Re: Topband: [PVRC] 2-element receiving arrays
It seems that padding the element capacitance as needed for equal capacitance would help. Dave KH6AQ On Thu, Mar 30, 2023 at 4:48 PM Frank W3LPL wrote: > Hi Dave, > > Anyone who has experimented with a high impedance antenna such > as an end fed half wave has experienced the extreme environmental > influence on the feedpoint impedance of a high impedance feed. > > The required spacing to trees and buildings is very difficult to predict > with any confidence. The impedance of a high impedance element > -- and hence the amount of voltag if feeds into the preamp -- > is heavily influenced by its immediate environment. > > If all of the high impedance verticals in an array do not produce the > same voltages from the signals received by the array, the pattern > of the array and especially its nulls are significantly degraded. > > 73 > Frank > W3LPL > > > > > > > > From: "K3ZJ David Siddall" > To: "Frank W3LPL" > Cc: "topband" , "PVRC" , > "Pete N4ZR N4ZR" > Sent: Friday, March 31, 2023 12:34:28 AM > Subject: Re: [PVRC] Topband: 2-element receiving arrays > > Frank, > " wrt to-negative effects of nearby trees and buildings." for high > impedance verticals: > > Is there any data measuring how much loss if placed in the woods? Minimum > distance from a tree to minimize the loss? Are their other effects too, > such as less directionality? > > 73, Dave K3ZJ > > > > On Thu, Mar 30, 2023 at 1:38 PM Frank W3LPL < [ mailto: > donov...@starpower.net | donov...@starpower.net ] > wrote: > > > Hi Pete, > > For a monoband receiving array, you might consider using low impedance > resonant verticals rather than high impedance verticals. > > The primary advantages of high impedance verticals are > - very short verticals (but taller verticals produce stronger signals) > - multi-band operation > - no radials > > The primary disadvantages are > - reliability issues with outdoor electronics > - lightning susceptibility of outdoor electronics > - higher cost > - much lower signal levels > - extreme care required to suppress common mode signals (buried feedlines > are highly recommended) > - negative effects of nearby trees and buildings. > > The primary advantages of low impedance verticals are > - much stronger signal levels > - much less criticality of common mode signal suppression, > - much lower cost > - much higher reliability > - immunity to lightning damage > - much less affected by nearby trees and buildings > > The primary disadvantages are > - taller verticals (typically about 24 feet) > - radials (they can be very short if many radials are used) > - mono band operation (switchable matching networks can be used for > multi-band operation). > > I highly recommend the DX Engineering Receiving Antenna Phasing System. > Its expensive but well worth the investment especially for a small array. > > [ https://www.dxengineering.com/parts/dxe-ncc-2 | > https://www.dxengineering.com/parts/dxe-ncc-2 ] > > If you have 120 feet for a three element array, the YCCC array is a great > choice > It can use high impedance or low impedance verticals > Unfortunately its no longer available from DX Engineering > The nine element YCCC array uses only three active elements at any time, > so its really a three element array switchable in many directions. > > [ > https://static.dxengineering.com/global/images/instructions/dxe-yccc-switch.pdf?_gl=1*1cv0fc9*_ga*MjEyMDA1Nzc3MS4xNjUyMzAyMjc0*_ga_NZB590FMHY*MTY4MDE5NTk1OC40My4xLjE2ODAxOTYwNTYuNTAuMC4w > | > https://static.dxengineering.com/global/images/instructions/dxe-yccc-switch.pdf?_gl=1*1cv0fc9*_ga*MjEyMDA1Nzc3MS4xNjUyMzAyMjc0*_ga_NZB590FMHY*MTY4MDE5NTk1OC40My4xLjE2ODAxOTYwNTYuNTAuMC4w > ] > > [ https://www.youtube.com/watch?v=dl-crM5Kb6A | > https://www.youtube.com/watch?v=dl-crM5Kb6A ] > > [ https://www.youtube.com/watch?v=lVW1CmrzP7c | > https://www.youtube.com/watch?v=lVW1CmrzP7c ] > > A two element array occupies only 60 feet or even a little less. > > 73 > Frank > W3LPL > > > - Original Message - > From: "Pete N4ZR N4ZR" < [ mailto:pete.n...@gmail.com | > pete.n...@gmail.com ] > > To: "topband" < [ mailto:Topband@contesting.com | Topband@contesting.com > ] > > Sent: Thursday, March 30, 2023 12:54:30 PM > Subject: Topband: 2-element receiving arrays > > Thinking ahead to next winter on 160, I'm interested in replacing my > K9AY Loop with a 2-vertical phased array. I'd like to homebrew the > antennas and just buy or build the remote control unit for the shack. > I'm looking for sources of components (antenna-located preamps and an > in-shack controller), and would prefer not to completely homebrew them, > but the prices at the usual suspects are awfully high. Any ideas? > > I have pretty reasonably-priced access to 25 and 31-foot fiberglass > poles (used for wind-socks by model airplane enthusiasts). I'm thinking > that one relatively low-cost approach might be to attach, say, #14 wire > to the poles, with preamps at the base, but wonder if there is a > downside to using such
Re: Topband: [PVRC] 2-element receiving arrays
Meaning, We do the best we can and there is no and there will never be a perfect solution. All we can do is attempt to eliminate as many variables as possible. My circle array works better than all of the other things I have tried. It is near fencing, close to a power line etc. I don't have unlimited flat land in the middle of nowhere. Not optimal but it is what I can do. I think people get caught up in perfection. Put up stuff and try it! You might be surprised. What works for me might not be a good solution for you, etc. W0MU On 3/30/2023 7:47 PM, Frank W3LPL wrote: Hi Dave, Anyone who has experimented with a high impedance antenna such as an end fed half wave has experienced the extreme environmental influence on the feedpoint impedance of a high impedance feed. The required spacing to trees and buildings is very difficult to predict with any confidence. The impedance of a high impedance element -- and hence the amount of voltag if feeds into the preamp -- is heavily influenced by its immediate environment. If all of the high impedance verticals in an array do not produce the same voltages from the signals received by the array, the pattern of the array and especially its nulls are significantly degraded. 73 Frank W3LPL Allow me to quibble a little with this analogy. The 1/2 wave dipole is a tuned circuit with a Q in the low double digits. This leverages any capacitance change. The voltage probe antenna is just a plain non-resonant capacitance. Still sensitive to nearby conductors, but probably not to the extent of the EFHW antenna. I would be more worried about circuit capacitance in the hi-Z preamp. In general, the capacitance of JFET's (or any FET's) is very loosely specified. The transconductance is also very loosely specified, and can act as a modulator of input capacitance due to the Miller effect. As if that isn't bad enough, the DXE preamp comes with tank circuits that you can optionally activate with jumpers. This adds another random variable to the input capacitance. Ideally, there would be a "factory select" padding capacitor to make the capacitance the same on all copies of the preamp. AFAIK, no preamps have this feature. And finally, the CB whip moves around wildly in the wind. If there are nearby objects, this adds a time variability. 73 Rick N6RK _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: [PVRC] 2-element receiving arrays
On 3/30/2023 7:47 PM, Frank W3LPL wrote: Hi Dave, Anyone who has experimented with a high impedance antenna such as an end fed half wave has experienced the extreme environmental influence on the feedpoint impedance of a high impedance feed. The required spacing to trees and buildings is very difficult to predict with any confidence. The impedance of a high impedance element -- and hence the amount of voltag if feeds into the preamp -- is heavily influenced by its immediate environment. If all of the high impedance verticals in an array do not produce the same voltages from the signals received by the array, the pattern of the array and especially its nulls are significantly degraded. 73 Frank W3LPL Allow me to quibble a little with this analogy. The 1/2 wave dipole is a tuned circuit with a Q in the low double digits. This leverages any capacitance change. The voltage probe antenna is just a plain non-resonant capacitance. Still sensitive to nearby conductors, but probably not to the extent of the EFHW antenna. I would be more worried about circuit capacitance in the hi-Z preamp. In general, the capacitance of JFET's (or any FET's) is very loosely specified. The transconductance is also very loosely specified, and can act as a modulator of input capacitance due to the Miller effect. As if that isn't bad enough, the DXE preamp comes with tank circuits that you can optionally activate with jumpers. This adds another random variable to the input capacitance. Ideally, there would be a "factory select" padding capacitor to make the capacitance the same on all copies of the preamp. AFAIK, no preamps have this feature. And finally, the CB whip moves around wildly in the wind. If there are nearby objects, this adds a time variability. 73 Rick N6RK _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: [PVRC] 2-element receiving arrays
Hi Dave, Anyone who has experimented with a high impedance antenna such as an end fed half wave has experienced the extreme environmental influence on the feedpoint impedance of a high impedance feed. The required spacing to trees and buildings is very difficult to predict with any confidence. The impedance of a high impedance element -- and hence the amount of voltag if feeds into the preamp -- is heavily influenced by its immediate environment. If all of the high impedance verticals in an array do not produce the same voltages from the signals received by the array, the pattern of the array and especially its nulls are significantly degraded. 73 Frank W3LPL From: "K3ZJ David Siddall" To: "Frank W3LPL" Cc: "topband" , "PVRC" , "Pete N4ZR N4ZR" Sent: Friday, March 31, 2023 12:34:28 AM Subject: Re: [PVRC] Topband: 2-element receiving arrays Frank, " wrt to-negative effects of nearby trees and buildings." for high impedance verticals: Is there any data measuring how much loss if placed in the woods? Minimum distance from a tree to minimize the loss? Are their other effects too, such as less directionality? 73, Dave K3ZJ On Thu, Mar 30, 2023 at 1:38 PM Frank W3LPL < [ mailto:donov...@starpower.net | donov...@starpower.net ] > wrote: Hi Pete, For a monoband receiving array, you might consider using low impedance resonant verticals rather than high impedance verticals. The primary advantages of high impedance verticals are - very short verticals (but taller verticals produce stronger signals) - multi-band operation - no radials The primary disadvantages are - reliability issues with outdoor electronics - lightning susceptibility of outdoor electronics - higher cost - much lower signal levels - extreme care required to suppress common mode signals (buried feedlines are highly recommended) - negative effects of nearby trees and buildings. The primary advantages of low impedance verticals are - much stronger signal levels - much less criticality of common mode signal suppression, - much lower cost - much higher reliability - immunity to lightning damage - much less affected by nearby trees and buildings The primary disadvantages are - taller verticals (typically about 24 feet) - radials (they can be very short if many radials are used) - mono band operation (switchable matching networks can be used for multi-band operation). I highly recommend the DX Engineering Receiving Antenna Phasing System. Its expensive but well worth the investment especially for a small array. [ https://www.dxengineering.com/parts/dxe-ncc-2 | https://www.dxengineering.com/parts/dxe-ncc-2 ] If you have 120 feet for a three element array, the YCCC array is a great choice It can use high impedance or low impedance verticals Unfortunately its no longer available from DX Engineering The nine element YCCC array uses only three active elements at any time, so its really a three element array switchable in many directions. [ https://static.dxengineering.com/global/images/instructions/dxe-yccc-switch.pdf?_gl=1*1cv0fc9*_ga*MjEyMDA1Nzc3MS4xNjUyMzAyMjc0*_ga_NZB590FMHY*MTY4MDE5NTk1OC40My4xLjE2ODAxOTYwNTYuNTAuMC4w | https://static.dxengineering.com/global/images/instructions/dxe-yccc-switch.pdf?_gl=1*1cv0fc9*_ga*MjEyMDA1Nzc3MS4xNjUyMzAyMjc0*_ga_NZB590FMHY*MTY4MDE5NTk1OC40My4xLjE2ODAxOTYwNTYuNTAuMC4w ] [ https://www.youtube.com/watch?v=dl-crM5Kb6A | https://www.youtube.com/watch?v=dl-crM5Kb6A ] [ https://www.youtube.com/watch?v=lVW1CmrzP7c | https://www.youtube.com/watch?v=lVW1CmrzP7c ] A two element array occupies only 60 feet or even a little less. 73 Frank W3LPL - Original Message - From: "Pete N4ZR N4ZR" < [ mailto:pete.n...@gmail.com | pete.n...@gmail.com ] > To: "topband" < [ mailto:Topband@contesting.com | Topband@contesting.com ] > Sent: Thursday, March 30, 2023 12:54:30 PM Subject: Topband: 2-element receiving arrays Thinking ahead to next winter on 160, I'm interested in replacing my K9AY Loop with a 2-vertical phased array. I'd like to homebrew the antennas and just buy or build the remote control unit for the shack. I'm looking for sources of components (antenna-located preamps and an in-shack controller), and would prefer not to completely homebrew them, but the prices at the usual suspects are awfully high. Any ideas? I have pretty reasonably-priced access to 25 and 31-foot fiberglass poles (used for wind-socks by model airplane enthusiasts). I'm thinking that one relatively low-cost approach might be to attach, say, #14 wire to the poles, with preamps at the base, but wonder if there is a downside to using such small-diameter antenna elements rather than 1 or 1.5 inch tubing? Alternatively, are clones of the DX Engineering 8' short verticals with preamps a good alternative? -- 73, Pete N4ZR _ Searchable Archives: [ http://www.contesting.com/_topband | http://www.contesting.com/
