Re: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series)
Again Eric, thanks for the advise. Today I got the Anaritsu sitemaster out and started playing with the return loss sweep into a couple different BpBr duplexers I had laying about. I put a 50 ohm load on one side of the T and the sitemaster cable on the other side. I swept the frequecy for return loss maximum db (lowest swr). I could really see the pass tuning in a much sharper light. On the sitemaster, the return loss looks very much like the notch does on the aeroflex's tracking generator. Is this what we want to see and tune the pass on the cans to? I do not have a network analyser, so the sitemaster and the tracking generator in the areoflex will just have to do. I am thinking that I need to use the sitemaster to tune each bandpass individually and then tweak after re-connecting the harness. Then use the areoflex's tracking generator to set the notches. Does this sound. About right? Thanks 73 de N5NPO Norm - Original Message - From: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com Sent: Mon Jul 27 21:51:01 2009 Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Norm, A Polyphaser does not put a DC ground on the center conductor of the feedline- nor does any other inline arrestor of any brand, except a quarter-wave shorted stub. But that is impractical at 2m. My point was simply that a single bandpass cavity on either the TX or the RX side, between the duplexer and the antenna tee, will put a DC ground on the feedline at the transmitter end. Most antennas are DC grounded, but a lot can happen to that feedline between the antenna and the duplexer. One 2m repeater I have on a hilltop suffered a lot from wind-caused static discharges (aka triboelectric charging) until I put a single bandpass cavity on the receive side. My intent was to prevent desense from the adjacent FM broadcast station, but the static elimination was a bonus. Regarding the determination of high pass versus low pass, this is usually determined by the design of the duplexer. Some designs are symmetrical, while others are asymmetrical. In most cases, the loop coupling will be different between the high side and the low side, so it is convenient to simply follow the manufacturer's settings, and their tuning instructions. In the case of the Sinclair Q202-G, the loop assemblies are all identical, and the notch tuning capacitors are the same as well, regardless of which pass side they're on. You're correct about bandpass duplexers being unsuitable for the 600 kHz split at 2m. However, I have a 8 bandpass duplexer on a commercial repeater that is using a 5.26 MHz split on VHF, and it works perfectly. I specified it because of the antenna being the high point on the tower, and I wanted DC ground at the duplexer for repeater protection. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of NORM KNAPP Sent: Monday, July 27, 2009 11:20 AM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: Re: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Again Eric Thanks for the wisdom and information. I will digest this over the next several days and when I can I am going to apply it. I have what I feel is a very good service monitor with tracking generator/spectrum analyzer. I have access to an Anritsu site master. It has a return loss bridge built in (I think) and I will give the low pass cans another go. The thing that I am curious about is what determins what side of the pass the notch will go? What makes a can a low pass can and not a high pass can? Does the value of ths capacitor do this? You mentioned the fact that BpBr duplexers don't have DC ground potential. I do have polyphasers and grounding pretty well covered. The repeater is at an old ATT Long lines microwave site. Grounding is not a problem. What were you saying about using bandpass only duplexers? I didn't think they were sharp enough for 600khz split. How many cans would you need to accomplish this and what are the advantages! I recently aquired another set of sinclair duplexers. They have no model info on them. They are high band VHF and are in the 154-158 range now. They were connected to a 250watt micor repeater. They apear to be hybrid ring type but they are small like 1/2 gallon milk carton sized and the harness has exposed braid between the cans (cartons) and the T's. They are mounted on a 19 rack panel with a cover. The cover is missing. The rack panel has the Sinclar tag and logo with ERP and the atom on it... Very strange. Again, I thank you for the wisdom and advice. 73 de N5NPO Norm - Original Message - From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com
RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series)
Eric, I was referring to commercial inline shorted-stub arrestors, such as those made Huber+Suhner, that typically are intended for use at 800 MHz and higher frequencies. I did not mean to imply that home-made quarter-wave stubs cannot be used. In fact, instructions for fabricating just such a device are found here: www.repeater-builder.com/ge/datafile-bulletin/df-10002-01.pdf 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Eric Grabowski Sent: Monday, July 27, 2009 10:30 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Eric, Why is a quarter-wave shorted stub impractical at 2m? I have been told that a quarter-wave shorted stub would serve two purposes: a) provide a dc path to ground for static caused by precip or wind, and also b) substantially reduce the strength of a transmitter's second harmonic. 73 and aloha, Eric KH6CQ --- On Mon, 7/27/09, Eric Lemmon wb6...@verizon.net wrote: From: Eric Lemmon wb6...@verizon.net Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) To: Repeater-Builder@yahoogroups.com Date: Monday, July 27, 2009, 4:51 PM Norm, A Polyphaser does not put a DC ground on the center conductor of the feedline- nor does any other inline arrestor of any brand, except a quarter-wave shorted stub. But that is impractical at 2m. My point was simply that a single bandpass cavity on either the TX or the RX side, between the duplexer and the antenna tee, will put a DC ground on the feedline at the transmitter end. Most antennas are DC grounded, but a lot can happen to that feedline between the antenna and the duplexer. One 2m repeater I have on a hilltop suffered a lot from wind-caused static discharges (aka triboelectric charging) until I put a single bandpass cavity on the receive side. My intent was to prevent desense from the adjacent FM broadcast station, but the static elimination was a bonus. Regarding the determination of high pass versus low pass, this is usually determined by the design of the duplexer. Some designs are symmetrical, while others are asymmetrical. In most cases, the loop coupling will be different between the high side and the low side, so it is convenient to simply follow the manufacturer' s settings, and their tuning instructions. In the case of the Sinclair Q202-G, the loop assemblies are all identical, and the notch tuning capacitors are the same as well, regardless of which pass side they're on. You're correct about bandpass duplexers being unsuitable for the 600 kHz split at 2m. However, I have a 8 bandpass duplexer on a commercial repeater that is using a 5.26 MHz split on VHF, and it works perfectly. I specified it because of the antenna being the high point on the tower, and I wanted DC ground at the duplexer for repeater protection. 73, Eric Lemmon WB6FLY snip all following
Re: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series)
But the GE file shows how to make a quarter-wave open-stub filter, not a shorted one. Chuck WB2EDV - Original Message - From: Eric Lemmon wb6...@verizon.net To: Repeater-Builder@yahoogroups.com Sent: Tuesday, July 28, 2009 9:06 PM Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Eric, I was referring to commercial inline shorted-stub arrestors, such as those made Huber+Suhner, that typically are intended for use at 800 MHz and higher frequencies. I did not mean to imply that home-made quarter-wave stubs cannot be used. In fact, instructions for fabricating just such a device are found here: www.repeater-builder.com/ge/datafile-bulletin/df-10002-01.pdf 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Eric Grabowski Sent: Monday, July 27, 2009 10:30 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Eric, Why is a quarter-wave shorted stub impractical at 2m? I have been told that a quarter-wave shorted stub would serve two purposes: a) provide a dc path to ground for static caused by precip or wind, and also b) substantially reduce the strength of a transmitter's second harmonic. 73 and aloha, Eric KH6CQ --- On Mon, 7/27/09, Eric Lemmon wb6...@verizon.net wrote: From: Eric Lemmon wb6...@verizon.net Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) To: Repeater-Builder@yahoogroups.com Date: Monday, July 27, 2009, 4:51 PM Norm, A Polyphaser does not put a DC ground on the center conductor of the feedline- nor does any other inline arrestor of any brand, except a quarter-wave shorted stub. But that is impractical at 2m. My point was simply that a single bandpass cavity on either the TX or the RX side, between the duplexer and the antenna tee, will put a DC ground on the feedline at the transmitter end. Most antennas are DC grounded, but a lot can happen to that feedline between the antenna and the duplexer. One 2m repeater I have on a hilltop suffered a lot from wind-caused static discharges (aka triboelectric charging) until I put a single bandpass cavity on the receive side. My intent was to prevent desense from the adjacent FM broadcast station, but the static elimination was a bonus. Regarding the determination of high pass versus low pass, this is usually determined by the design of the duplexer. Some designs are symmetrical, while others are asymmetrical. In most cases, the loop coupling will be different between the high side and the low side, so it is convenient to simply follow the manufacturer' s settings, and their tuning instructions. In the case of the Sinclair Q202-G, the loop assemblies are all identical, and the notch tuning capacitors are the same as well, regardless of which pass side they're on. You're correct about bandpass duplexers being unsuitable for the 600 kHz split at 2m. However, I have a 8 bandpass duplexer on a commercial repeater that is using a 5.26 MHz split on VHF, and it works perfectly. I specified it because of the antenna being the high point on the tower, and I wanted DC ground at the duplexer for repeater protection. 73, Eric Lemmon WB6FLY snip all following Yahoo! Groups Links
RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series)
Chuck, Perhaps we're splitting hairs, because the text in that bulletin states To the spurious, the stub looks like a short... I agree that my choice of words leaves unclear the difference between looks like a short and is a short. Is it too late to invoke that handy disclaimer of vagueness, YMMV? -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey Sent: Tuesday, July 28, 2009 6:25 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) But the GE file shows how to make a quarter-wave open-stub filter, not a shorted one. Chuck WB2EDV - Original Message - From: Eric Lemmon wb6...@verizon.net mailto:wb6fly%40verizon.net To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Tuesday, July 28, 2009 9:06 PM Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Eric, I was referring to commercial inline shorted-stub arrestors, such as those made Huber+Suhner, that typically are intended for use at 800 MHz and higher frequencies. I did not mean to imply that home-made quarter-wave stubs cannot be used. In fact, instructions for fabricating just such a device are found here: www.repeater-builder.com/ge/datafile-bulletin/df-10002-01.pdf 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of Eric Grabowski Sent: Monday, July 27, 2009 10:30 PM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Eric, Why is a quarter-wave shorted stub impractical at 2m? I have been told that a quarter-wave shorted stub would serve two purposes: a) provide a dc path to ground for static caused by precip or wind, and also b) substantially reduce the strength of a transmitter's second harmonic. 73 and aloha, Eric KH6CQ --- On Mon, 7/27/09, Eric Lemmon wb6...@verizon.net mailto:wb6fly%40verizon.net wrote: From: Eric Lemmon wb6...@verizon.net mailto:wb6fly%40verizon.net Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Date: Monday, July 27, 2009, 4:51 PM Norm, A Polyphaser does not put a DC ground on the center conductor of the feedline- nor does any other inline arrestor of any brand, except a quarter-wave shorted stub. But that is impractical at 2m. My point was simply that a single bandpass cavity on either the TX or the RX side, between the duplexer and the antenna tee, will put a DC ground on the feedline at the transmitter end. Most antennas are DC grounded, but a lot can happen to that feedline between the antenna and the duplexer. One 2m repeater I have on a hilltop suffered a lot from wind-caused static discharges (aka triboelectric charging) until I put a single bandpass cavity on the receive side. My intent was to prevent desense from the adjacent FM broadcast station, but the static elimination was a bonus. Regarding the determination of high pass versus low pass, this is usually determined by the design of the duplexer. Some designs are symmetrical, while others are asymmetrical. In most cases, the loop coupling will be different between the high side and the low side, so it is convenient to simply follow the manufacturer' s settings, and their tuning instructions. In the case of the Sinclair Q202-G, the loop assemblies are all identical, and the notch tuning capacitors are the same as well, regardless of which pass side they're on. You're correct about bandpass duplexers being unsuitable for the 600 kHz split at 2m. However, I have a 8 bandpass duplexer on a commercial repeater that is using a 5.26 MHz split on VHF, and it works perfectly. I specified it because of the antenna being the high point on the tower, and I wanted DC ground at the duplexer for repeater protection. 73, Eric Lemmon WB6FLY snip all following Yahoo! Groups Links
Re: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series)
I know I'm not trying to split hairs, but I believe the concern was to actually use a DC shorted stub to help keep transmission line surges shunted. You'd suggested a bandpass can, which works. Anyway, that's why I jumped in. Chuck WB2EDV - Original Message - From: Eric Lemmon wb6...@verizon.net To: Repeater-Builder@yahoogroups.com Sent: Tuesday, July 28, 2009 9:41 PM Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Chuck, Perhaps we're splitting hairs, because the text in that bulletin states To the spurious, the stub looks like a short... I agree that my choice of words leaves unclear the difference between looks like a short and is a short. Is it too late to invoke that handy disclaimer of vagueness, YMMV?
Re: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series)
Again Eric Thanks for the wisdom and information. I will digest this over the next several days and when I can I am going to apply it. I have what I feel is a very good service monitor with tracking generator/spectrum analyzer. I have access to an Anaritsu site master. It has a return loss bridge built in (I think) and I will give the low pass cans another go. The thing that I am curious about is what determins what side of the pass the notch will go? What makes a can a low pass can and not a high pass can? Does the value of ths capacitor do this? You mentioned the fact that BpBr duplexers don't have DC ground potential. I do have polyphasers and grounding pretty well covered. The repeater is at an old ATT Long lines microwave site. Grounding is not a problem. What were you saying about using bandpass only duplexers? I didn't think they were sharp enough for 600khz split. How many cans would you need to accomplish this and what are the advantages! I recently aquired another set of sinclair duplexers. They have no model info on them. They are high band VHF and are in the 154-158 range now. They were connected to a 250watt micor repeater. They apear to be hybrid ring type but they are small like 1/2 gallon milk carton sized and the harness has exposed braid between the cans (cartons) and the T's. They are mounted on a 19 rack panel with a cover. The cover is missing. The rack panel has the Sinclar tag and logo with ERP and the atom on it... Very strange. Again, I thank you for the wisdom and advise. 73 de N5NPO Norm - Original Message - From: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com Sent: Sun Jul 26 11:20:33 2009 Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Norm, Thanks for the update on your quest. The loops have two adjustments, and they are not complementary. The degree of coupling, and the amount of insertion loss, is adjusted by loosening the three screws that secure the loop mounting plate, and turning the plate slightly to achieve the desired insertion loss- which is generally around 0.5 to 0.8 dB per can. The variable capacitor mounted in the loop plate is used to move the notch closer to, or away from, the bandpass peak. Are you following the Q202G tuning instructions shown on the RBTIP? Those instructions are here: www.repeater-builder.com/sinclair/ci-1069-Q-Series-Tuning.pdf Because the bandpass peak is so vague, the best way to tune it is to use a network analyzer or a spectrum analyzer with a return-loss bridge. When tuning for return loss, the image on the display is a very sharp notch which is easy to get right on the money. Then, the analyzer is switched to transmission loss to set the notch capacitor. Finally, the loop plate is rotated to achieve an insertion loss of between 0.5 and 0.8 dB. If the jumper cables between each pair of cans are the correct length, the insertion losses should add exactly. I normally go through this routine at least three times to get the tuning as good as I can. I looked at some Q202G loops from a 2m duplexer, and they are plain copper- not silver-plated. The standard VHF loop assembly has a 1/4 wide copper strap bent into a rectangle that measures about 1-1/8 by 3-1/8, so if your loops are much different in size, they may be unsuitable for 2m operation. The notch tuning capacitor is a Johanson 5602, which is rated 1 to 30 pF, and has a Q of greater than 800. I have to wonder if the added capacitors you found were high-Q silver micas or ordinary ceramic capacitors. If the latter, the cavity cannot be tuned properly. The Johanson capacitors are on page 4 of this brochure: www.johansonmfg.com/pdf/Air-Capacitor.pdf One thing to keep in mind about BpBr duplexers- and not just those made by Sinclair- is that the presence of the notch tuning capacitor means that there is no DC ground anywhere on the feedline between the antenna and the receiver. A high-voltage spike caused by a nearby lightning strike, or an electrical system fault, can sail right into the receiver front end. That's one good reason for having a true bandpass cavity- which has DC grounded loops- somewhere in the RF chain. I have heard a few reports of notch tuning capacitors that were destroyed by high-voltage arcing. This damage would not be visible. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of NORM KNAPP Sent: Sunday, July 26, 2009 3:58 AM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Ok, it is official. I have a set of sinclair Q202 duplexers that didn't come as a set. At least two of the cans have different serial numbers and different factory
RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series)
Norm, A Polyphaser does not put a DC ground on the center conductor of the feedline- nor does any other inline arrestor of any brand, except a quarter-wave shorted stub. But that is impractical at 2m. My point was simply that a single bandpass cavity on either the TX or the RX side, between the duplexer and the antenna tee, will put a DC ground on the feedline at the transmitter end. Most antennas are DC grounded, but a lot can happen to that feedline between the antenna and the duplexer. One 2m repeater I have on a hilltop suffered a lot from wind-caused static discharges (aka triboelectric charging) until I put a single bandpass cavity on the receive side. My intent was to prevent desense from the adjacent FM broadcast station, but the static elimination was a bonus. Regarding the determination of high pass versus low pass, this is usually determined by the design of the duplexer. Some designs are symmetrical, while others are asymmetrical. In most cases, the loop coupling will be different between the high side and the low side, so it is convenient to simply follow the manufacturer's settings, and their tuning instructions. In the case of the Sinclair Q202-G, the loop assemblies are all identical, and the notch tuning capacitors are the same as well, regardless of which pass side they're on. You're correct about bandpass duplexers being unsuitable for the 600 kHz split at 2m. However, I have a 8 bandpass duplexer on a commercial repeater that is using a 5.26 MHz split on VHF, and it works perfectly. I specified it because of the antenna being the high point on the tower, and I wanted DC ground at the duplexer for repeater protection. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of NORM KNAPP Sent: Monday, July 27, 2009 11:20 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Again Eric Thanks for the wisdom and information. I will digest this over the next several days and when I can I am going to apply it. I have what I feel is a very good service monitor with tracking generator/spectrum analyzer. I have access to an Anritsu site master. It has a return loss bridge built in (I think) and I will give the low pass cans another go. The thing that I am curious about is what determins what side of the pass the notch will go? What makes a can a low pass can and not a high pass can? Does the value of ths capacitor do this? You mentioned the fact that BpBr duplexers don't have DC ground potential. I do have polyphasers and grounding pretty well covered. The repeater is at an old ATT Long lines microwave site. Grounding is not a problem. What were you saying about using bandpass only duplexers? I didn't think they were sharp enough for 600khz split. How many cans would you need to accomplish this and what are the advantages! I recently aquired another set of sinclair duplexers. They have no model info on them. They are high band VHF and are in the 154-158 range now. They were connected to a 250watt micor repeater. They apear to be hybrid ring type but they are small like 1/2 gallon milk carton sized and the harness has exposed braid between the cans (cartons) and the T's. They are mounted on a 19 rack panel with a cover. The cover is missing. The rack panel has the Sinclar tag and logo with ERP and the atom on it... Very strange. Again, I thank you for the wisdom and advice. 73 de N5NPO Norm - Original Message - From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Sun Jul 26 11:20:33 2009 Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Norm, Thanks for the update on your quest. The loops have two adjustments, and they are not complementary. The degree of coupling, and the amount of insertion loss, is adjusted by loosening the three screws that secure the loop mounting plate, and turning the plate slightly to achieve the desired insertion loss- which is generally around 0.5 to 0.8 dB per can. The variable capacitor mounted in the loop plate is used to move the notch closer to, or away from, the bandpass peak. Are you following the Q202G tuning instructions shown on the RBTIP? Those instructions are here: www.repeater-builder.com/sinclair/ci-1069-Q-Series-Tuning.pdf Because the bandpass peak is so vague, the best way to tune it is to use a network analyzer or a spectrum analyzer with a return-loss bridge. When tuning for return loss, the image on the display is a very sharp notch which is easy to get right on the money. Then, the analyzer is switched to transmission loss to set the notch capacitor
RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series)
Eric, Why is a quarter-wave shorted stub impractical at 2m? I have been told that a quarter-wave shorted stub would serve two purposes: a) provide a dc path to ground for static caused by precip or wind, and also b) substantially reduce the strength of a transmitter's second harmonic. 73 and aloha, Eric KH6CQ --- On Mon, 7/27/09, Eric Lemmon wb6...@verizon.net wrote: From: Eric Lemmon wb6...@verizon.net Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) To: Repeater-Builder@yahoogroups.com Date: Monday, July 27, 2009, 4:51 PM Norm, A Polyphaser does not put a DC ground on the center conductor of the feedline- nor does any other inline arrestor of any brand, except a quarter-wave shorted stub. But that is impractical at 2m. My point was simply that a single bandpass cavity on either the TX or the RX side, between the duplexer and the antenna tee, will put a DC ground on the feedline at the transmitter end. Most antennas are DC grounded, but a lot can happen to that feedline between the antenna and the duplexer. One 2m repeater I have on a hilltop suffered a lot from wind-caused static discharges (aka triboelectric charging) until I put a single bandpass cavity on the receive side. My intent was to prevent desense from the adjacent FM broadcast station, but the static elimination was a bonus. Regarding the determination of high pass versus low pass, this is usually determined by the design of the duplexer. Some designs are symmetrical, while others are asymmetrical. In most cases, the loop coupling will be different between the high side and the low side, so it is convenient to simply follow the manufacturer' s settings, and their tuning instructions. In the case of the Sinclair Q202-G, the loop assemblies are all identical, and the notch tuning capacitors are the same as well, regardless of which pass side they're on. You're correct about bandpass duplexers being unsuitable for the 600 kHz split at 2m. However, I have a 8 bandpass duplexer on a commercial repeater that is using a 5.26 MHz split on VHF, and it works perfectly. I specified it because of the antenna being the high point on the tower, and I wanted DC ground at the duplexer for repeater protection. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@ yahoogroups. com [mailto:Repeater-Builder@ yahoogroups. com] On Behalf Of NORM KNAPP Sent: Monday, July 27, 2009 11:20 AM To: Repeater-Builder@ yahoogroups. com Subject: Re: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Again Eric Thanks for the wisdom and information. I will digest this over the next several days and when I can I am going to apply it. I have what I feel is a very good service monitor with tracking generator/spectrum analyzer. I have access to an Anritsu site master. It has a return loss bridge built in (I think) and I will give the low pass cans another go. The thing that I am curious about is what determins what side of the pass the notch will go? What makes a can a low pass can and not a high pass can? Does the value of ths capacitor do this? You mentioned the fact that BpBr duplexers don't have DC ground potential. I do have polyphasers and grounding pretty well covered. The repeater is at an old ATT Long lines microwave site. Grounding is not a problem. What were you saying about using bandpass only duplexers? I didn't think they were sharp enough for 600khz split. How many cans would you need to accomplish this and what are the advantages! I recently aquired another set of sinclair duplexers. They have no model info on them. They are high band VHF and are in the 154-158 range now. They were connected to a 250watt micor repeater. They apear to be hybrid ring type but they are small like 1/2 gallon milk carton sized and the harness has exposed braid between the cans (cartons) and the T's. They are mounted on a 19 rack panel with a cover. The cover is missing. The rack panel has the Sinclar tag and logo with ERP and the atom on it... Very strange. Again, I thank you for the wisdom and advice. 73 de N5NPO Norm - Original Message - From: Repeater-Builder@ yahoogroups. com mailto:Repeater- Builder%40yahoog roups.com Repeater-Builder@ yahoogroups. com mailto:Repeater- Builder%40yahoog roups.com To: Repeater-Builder@ yahoogroups. com mailto:Repeater- Builder%40yahoog roups.com Repeater-Builder@ yahoogroups. com mailto:Repeater- Builder%40yahoog roups.com Sent: Sun Jul 26 11:20:33 2009 Subject: RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Norm, Thanks for the update on your quest. The loops have two adjustments, and they are not complementary. The degree of coupling, and the amount of insertion loss, is adjusted by loosening the three screws that secure the loop mounting plate, and turning the plate slightly to achieve
RE: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series)
Norm, Thanks for the update on your quest. The loops have two adjustments, and they are not complementary. The degree of coupling, and the amount of insertion loss, is adjusted by loosening the three screws that secure the loop mounting plate, and turning the plate slightly to achieve the desired insertion loss- which is generally around 0.5 to 0.8 dB per can. The variable capacitor mounted in the loop plate is used to move the notch closer to, or away from, the bandpass peak. Are you following the Q202G tuning instructions shown on the RBTIP? Those instructions are here: www.repeater-builder.com/sinclair/ci-1069-Q-Series-Tuning.pdf Because the bandpass peak is so vague, the best way to tune it is to use a network analyzer or a spectrum analyzer with a return-loss bridge. When tuning for return loss, the image on the display is a very sharp notch which is easy to get right on the money. Then, the analyzer is switched to transmission loss to set the notch capacitor. Finally, the loop plate is rotated to achieve an insertion loss of between 0.5 and 0.8 dB. If the jumper cables between each pair of cans are the correct length, the insertion losses should add exactly. I normally go through this routine at least three times to get the tuning as good as I can. I looked at some Q202G loops from a 2m duplexer, and they are plain copper- not silver-plated. The standard VHF loop assembly has a 1/4 wide copper strap bent into a rectangle that measures about 1-1/8 by 3-1/8, so if your loops are much different in size, they may be unsuitable for 2m operation. The notch tuning capacitor is a Johanson 5602, which is rated 1 to 30 pF, and has a Q of greater than 800. I have to wonder if the added capacitors you found were high-Q silver micas or ordinary ceramic capacitors. If the latter, the cavity cannot be tuned properly. The Johanson capacitors are on page 4 of this brochure: www.johansonmfg.com/pdf/Air-Capacitor.pdf One thing to keep in mind about BpBr duplexers- and not just those made by Sinclair- is that the presence of the notch tuning capacitor means that there is no DC ground anywhere on the feedline between the antenna and the receiver. A high-voltage spike caused by a nearby lightning strike, or an electrical system fault, can sail right into the receiver front end. That's one good reason for having a true bandpass cavity- which has DC grounded loops- somewhere in the RF chain. I have heard a few reports of notch tuning capacitors that were destroyed by high-voltage arcing. This damage would not be visible. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of NORM KNAPP Sent: Sunday, July 26, 2009 3:58 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Sinclair Q202 duplexers (frankenstein series) Ok, it is official. I have a set of sinclair Q202 duplexers that didn't come as a set. At least two of the cans have different serial numbers and different factory tuned frequncies. DRAT! Ok, so here is the problem. With my trusty Aeroflex 2945 (I think that is the model) I can easily get a -35dB notch on each of the hi pass cans at 147.825 pass and 147.225 notch. No problem with that side. Ok, the problem is on the low pass pair (mix-mached I am sure). I can barely get a -30dB notch on each can even if I spin the loops. So, just out of (morbid) curiocity, I pulled the loop out of one just to show a fellow ham what was in there. Lo and behold there was a 12pF cap soldered accoss the notch tune cap. H... What would happen if I took this cap off there since to get the -30dB notch the tuning cap is almost screwed all the way out (min capacitance). So I got out the soldering iron and removed it. It worked, sort of. I was able to get a -35dB notch on my lo pass (147.225 pass 147.825 notch) side, but at the expense of some pass loss higher than the high pass side. What happend is it seemed to make the low pass can into a high pass can. The notch went to the other side of the pass. I spun the loop to get the best result and tuned the notch cap near its max capacitance to get the notch where it should be. It worked barely and with a bit more loss in the pass. I am thinkin I may need to go back and put a 6pF cap accross the notch tune to get it where I want it, but I am not sure. On the second can of the lo pass high notch side I tried to remove the cap, but it didn't turn out the same. The loop inside it was not silver plated like the previous can, it was just plain copper and appeared to be a bit longer. When I removed the cap on this can, the notch went to the low side of the pass and I couldn't get it to come back around. I will definitly have to try a 6pF cap accross the notch tune cap on this one. Now, I just replaced the harness with RG-214/U jumpers the length needed to get 14 between centers of the Tee's. The old ones were RG-142/U and were also apparently the correct
