Re: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due...
Skipp - Looking at the cabling - TX side is normal; but the receive side looks to be wired as 2 - 3 can duplexers in parallel. How does this improve rejection? Seems that IF you needed the parallel duplexers to handle a LOT of tx power, that would be okay, but does it help on the receive side? Just wondering . . . Chas, KS3Z --- skipp025 [EMAIL PROTECTED] wrote: Re: When 4, 6 or 8 Cavities just won't due... Another Ebay gem: DB PRODUCTS 9-CAVITY RADIO REPEATER DUPLEXER-100DB-HAM Ebay Item number: 250120910164 I don't know to be impressed or just laugh at all the hardware (number of cavities used). cheers, skipp Yahoo! Groups Links (Yahoo! ID required) mailto:[EMAIL PROTECTED] Yahoo! oneSearch: Finally, mobile search that gives answers, not web links. http://mobile.yahoo.com/mobileweb/onesearch?refer=1ONXIC
Re: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due...
And they only approached 100 dB... Chuck WB2EDV - Original Message - From: skipp025 [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, May 28, 2007 3:02 AM Subject: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due... Re: When 4, 6 or 8 Cavities just won't due... Another Ebay gem: DB PRODUCTS 9-CAVITY RADIO REPEATER DUPLEXER-100DB-HAM Ebay Item number: 250120910164 I don't know to be impressed or just laugh at all the hardware (number of cavities used). cheers, skipp Yahoo! Groups Links
Re: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due...
It would seem like the middle and right columns were originally a simple duplexer, then they added the left column to that. If you can trust the labeling, the bottom left is the TX input and the top right is the RX input. The middle and left columns have shorted loop stubs attached to each cavity. These are stuffed down between the cavities and you can see the shorted ends on a couple. The right column doesn't have these stubs. The signal path seems to go from the bottom middle column, up to the top middle, then over to the top left and down to the bottom left. The blue sticker shown seems to be for the 152-153 MHz range, although that could have been for just the left column's cavities. It only shows one pass freq and one reject freq; a duplexer would have a high-pass and a low-pass; this looks more like a specially designed filter than a real duplexer, although there are labels on the top middle and top right cavities indicating RX and TX respectively. It's strange that the left and middle columns are configured differently, with short pieces of coax between the TEE fittings and the cavities in the middle column that are not present on the left column. Bob M. == --- skipp025 [EMAIL PROTECTED] wrote: Re: When 4, 6 or 8 Cavities just won't due... Another Ebay gem: DB PRODUCTS 9-CAVITY RADIO REPEATER DUPLEXER-100DB-HAM Ebay Item number: 250120910164 I don't know to be impressed or just laugh at all the hardware (number of cavities used). cheers, skipp Take the Internet to Go: Yahoo!Go puts the Internet in your pocket: mail, news, photos more. http://mobile.yahoo.com/go?refer=1GNXIC
Re: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due...
What no one has mentioned yet is that the cans all appear to be NOTCH cans. DB had some variations of the notches that were skewed to one side of the notch or the other. It is possible that this was speced as a special product to take out specific freq ranges while leaving a wide open pass range. If nothing else it should be a good source of notch cans. Milt N3LTQ - Original Message - From: skipp025 [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, May 28, 2007 3:02 AM Subject: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due... Re: When 4, 6 or 8 Cavities just won't due... Another Ebay gem: DB PRODUCTS 9-CAVITY RADIO REPEATER DUPLEXER-100DB-HAM Ebay Item number: 250120910164 I don't know to be impressed or just laugh at all the hardware (number of cavities used). cheers, skipp Yahoo! Groups Links
Re: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due...
I too was trying to figure out the harness. I've never seen something like this before. I also saw only 3 cans in the transmit side. This must be a low power duplexer, as these appear to be only a notch devices and there are only 3 cans to notch out the transmitter noise from getting into the receiver. The six cans on the receive side probably are tuned to notch the transmitter frequency out of the receiver. Any transmitter noise that is on the receiver input would not be filtered out in the receiver cans. 73, Joe, K1ike -- Original message -- From: Charles Schmell [EMAIL PROTECTED] Skipp - Looking at the cabling - TX side is normal; but the receive side looks to be wired as 2 - 3 can duplexers in parallel. How does this improve rejection? Seems that IF you needed the parallel duplexers to handle a LOT of tx power, that would be okay, but does it help on the receive side? Just wondering . . . Chas, KS3Z ---BeginMessage--- Skipp - Looking at the cabling - TX side is normal; but the receive side looks to be wired as 2 - 3 can duplexers in parallel. How does this improve rejection? Seems that IF you needed the parallel duplexers to handle a LOT of tx power, that would be okay, but does it help on the receive side? Just wondering . . . Chas, KS3Z --- skipp025 [EMAIL PROTECTED]com wrote: Re: When 4, 6 or 8 Cavities just won't due... Another Ebay gem: DB PRODUCTS 9-CAVITY RADIO REPEATER DUPLEXER-100DB-HAM Ebay Item number: 250120910164 I don't know to be impressed or just laugh at all the hardware (number of cavities used). cheers, skipp Yahoo! Groups Links (Yahoo! ID required) mailto:Repeater-Builder-fullfeatured@yahoogroups.com __Yahoo! oneSearch: Finally, mobile search that gives answers, not web links. http://mobile.yahoo.com/mobileweb/onesearch?refer=1ONXIC ---End Message---
RE: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due...
It started out as a stock six-cavity notch duplexer (I have one of these in storage - I think it's a DB-4021?). Let me explain that part (the stock duplexer) first. Before I get into it, realize that some notch cavities are asymmetrical in terms of the notch response - they have somewhat of a high-pass *or* low-pass characteristic to them. That is, the insertion loss above the notch frequency may be a few dB more than it is below the notch. To start with, the three cavities on the right are one side of the duplexer, and the three in the middle are the other side. Easy enough. The three cavities on the right have traditional tees right on the loops. The three in the middle have the cavities stood off what would normally be a tee using a length of coax. In other words, instead of the tee along the length of the harness being attached directly to the cavity loop, there is a short piece of coax between the tee and the cavity loop. By standing the cavity off by a length of cable (typically 1/4 wave), the high-pass or low-pass characteristic of the cavity is flipped. So, if we assume the right three cavities were high-pass, the middle three would be low pass using this technique. Now, to get back to the stubs. They are added right at the cavity tee to provide additional notch depth and enhance the high-pass/low-pass response. Depending on the length of the cable, they can look like either L or C in parallel with the loop. So, that explains the duplexer. That leaves the three cavities on the left. Those are just more notch cavities, again with the stubs to enhance the response. HOWEVER, like Bob, what bothers me is that these three extra cavities are configured without the standoff coax between the tee and the cavity, thereby making them the same pass-response configuration as the RIGHT three cavities, whereas they should be configured the same as the MIDDLE three cavities. Not sure what to make of that...my guess would be that it doesn't work right... --- Jeff -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Monday, May 28, 2007 8:04 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due... It would seem like the middle and right columns were originally a simple duplexer, then they added the left column to that. If you can trust the labeling, the bottom left is the TX input and the top right is the RX input. The middle and left columns have shorted loop stubs attached to each cavity. These are stuffed down between the cavities and you can see the shorted ends on a couple. The right column doesn't have these stubs. The signal path seems to go from the bottom middle column, up to the top middle, then over to the top left and down to the bottom left. The blue sticker shown seems to be for the 152-153 MHz range, although that could have been for just the left column's cavities. It only shows one pass freq and one reject freq; a duplexer would have a high-pass and a low-pass; this looks more like a specially designed filter than a real duplexer, although there are labels on the top middle and top right cavities indicating RX and TX respectively. It's strange that the left and middle columns are configured differently, with short pieces of coax between the TEE fittings and the cavities in the middle column that are not present on the left column. Bob M. == --- skipp025 [EMAIL PROTECTED] wrote: Re: When 4, 6 or 8 Cavities just won't due... Another Ebay gem: DB PRODUCTS 9-CAVITY RADIO REPEATER DUPLEXER-100DB-HAM Ebay Item number: 250120910164 I don't know to be impressed or just laugh at all the hardware (number of cavities used). cheers, skipp __ __Take the Internet to Go: Yahoo!Go puts the Internet in your pocket: mail, news, photos more. http://mobile.yahoo.com/go?refer=1GNXIC Yahoo! Groups Links No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.472 / Virus Database: 269.8.0/821 - Release Date: 5/27/2007 3:05 PM
RE: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due...
* Re: When 4, 6 or 8 Cavities just won't due... Another Ebay gem: DB PRODUCTS 9-CAVITY RADIO REPEATER DUPLEXER-100DB-HAM Ebay Item number: 250120910164 I don't know to be impressed or just laugh at all the hardware (number of cavities used). cheers, skipp * The description says it was for an amateur project that was never completed, and I can see why. This setup has three notch cans in the transmit side, and 6 notch cans in the receive side. As described, yes, the insertion loss would be pretty low, however with no band pass protection for the front end of the receiver, you better be on your own hilltop with no one else around. I don't think this custom assembly qualifies much as a duplexer, but it is a nice assembly of notch cavities. * 73 N7HQR,_._,___
RE: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due...
It looks to me that the extra cavities were added to a regular duplexer. The receive side has the T connector connected to the notch cavity thru a length of cable to make a pass band network along with the notch. This has the effect of skewing the normal pass of the notch filter on one side (making for a steeper notch on one side) and at the same time forming somewhat of a pass band filter with the length of cable between the filter and T. The extra stub I believe is used to try and make the notch steeper on one side so as not to overlap on the TX side with the close spacing. They may have reduced the coupling of the notches in order to try and make them steeper for the close spacing and then added the extra cavities to make up for the inadequate coupling in the primary filter cans. Or they may have just thought that more is better. Or they may have added the extra filters because of the botched job of trying to make a close space duplexer and not getting the cables right. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of skipp025 Sent: Monday, May 28, 2007 2:03 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due... Re: When 4, 6 or 8 Cavities just won't due... Another Ebay gem: DB PRODUCTS 9-CAVITY RADIO REPEATER DUPLEXER-100DB-HAM Ebay Item number: 250120910164 I don't know to be impressed or just laugh at all the hardware (number of cavities used). cheers, skipp Yahoo! Groups Links
