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Honestly I suspect duplexer issues. Possibly in moving to a new location it was knocked out of tune. I bought a spectrum analyzer so I can tune duplexers, circulators, etc., but if you don't have one or access to one you'll need to carry it to a shop that can check the tuning.

The new duplexer is many times better that even a six can mobile duplexer, period. With both bandpass and reject that will dump -95dB, and only -1.2 dB insertion loss (compared to -2.2 dB loss with the mobile duplexer), it should boost my receive sensitivity quite a bit. No splicing will be needed for the heliax either, since I seem to have overestimated how much I'd need by about 20' or possibly a bit more... <oops!> The problem is that I cannot raise the antenna another 10' even without having to resort to guy wires.

Update: I won the bidding war for the DB duplexer, but one SOB pushed the price up with six consecutive bids trying to hit my max limit, darn it! From $188 to $268 needlessly... ...ah well, it should arrive next Thursday.

The auction of the DB duplexer won't end for another 17 hours and a few minutes. I'm still the high bidder but have a max bid sufficiently high to probably get it. I'll keep my eyes on it just in case though. The specs on that model are outstanding -95dB reject, -1.2dB insertion loss: http://www.repeater-builder.com/antenna/db/pdfs/db-4076-duplexers.pdf I shouldn't need it, but I do have a 100 watt Henry amp I can drive up to 50 watts if necessary. Corey, the mobile duplexer is undoubtedly the proximate cause of the performance, as it has about -2.5dB insertion loss. If I can at least get it to hear as far as it transmits, I'll be more satisfied. I just got home from shipping the dual CDM-1550 repeater to its new home in Boonsville, NC and was chatting with a fellow ham/gmrs user. He's running 4watts into a simple antenna up about 17' and was easily 95% full quieting into the repeater. He had solid copy from my 45 watt mobile up to around 10' miles from the repeater with the rear of my car (minor lobe) aimed at the antenna, so that's about what I expected. I could still copy the repeater at full quieting at 14 miles LOS from the repeater. Again, just about what we've projected.

Okay, final update on this saga. I received the BCR-40U back yesterday afternoon, which was remarkably good timing since a fellow on eBay won the bidding on the unit in the picture above and I needed to box it up for shipment later today. The new duplexer has made a not insignificant difference (note the use of syntax and qualifiers). While it is better, it's still not as good as I'd like, but it is as good as it's going to get with my limited antenna height and HAAT of a mere 22' on average. I was awakened this morning by the sounds of two friends chatting on my repeater, which was a pleasant surprise. One was mobile (meaning his HT was connected to a mag mount antenna, and the other was just using his HT. Eventually they switched to the "Munster 600" repeater, which with it's 4 bay DB antenna at the top of a 100' tower gave them both full quieting. Unfortunately that repeater's transmitter is slowly dying and gets quite noisy as it heats up. I've got to route a new RG-214 jumper from the antenna's lightning protector into the shack and then I'm just going to leave it running until I find a new home for it.

UPDATE: I received an email from Ron this morning. The new duplexer was installed and... Unit has been shipped this morning and should arrive Thursday by end of day. I'm looking forward to putting it through its paces. In the meantime, I've placed a bid on a Decibel DB4076W-A bandpass/reject duplexer to keep on hand in case it's needed. That with a receiver preamp and my Henry amp should solve any future issues I should think!

So am I Corey, so am I... ...I'm also a bit shocked that apparently I know more about duplexers (which isn't all that much) than the engineer who designed and built the repeater.

My reply to Ron: Incidentally, I received a reply just now that a new duplexer has been ordered, and should arrive in about three days. Then he'll tune it up, install it, and test thoroughly before returning it to me. <fingers-crossed-mode:ON>

I got an email from Ron this morning with his findings:

That is the same antenna that I'm running, although mine is fed with 60' of Comspec 1/2" heliax. Have you access to an antenna analyzer? If so, sweep the system at both your transmit and receive frequencies to see what the precise VSWR and impedance are.

I feel your pain! That would seriously annoy me as well.

The BridgeCom Systems BCR-40U is on it's way back home for a hopefully successful operation and rapid recovery. It cost $50.45 to ship that 21 lbs of dead weight. <sigh> The irony is that the "home-brew repeater" that I'd cobbled together which I've put on-line in the interim, works just as good as, actually perhaps a little better than the very expensive, deaf repeater! I was about 8 miles from the repeater's antenna and was able to get full quieting from both my 4 watt HTs! http://puu.sh/ovIft.jpg

Thanks for the comments. Yes, height is definitely "king" and there's simply no way around that. In retrospect, I have gone about this entire project bass-ackwards from the beginning. I should have secured a tower or building for an antenna site first, then invested in the equipment. Since it's too late now, I'll send the Bridgecom in for a doctor's visit, and continue searching for a home for it. In the meantime I'll just have to accept limited coverage. If I can get the ears to work roughly equivalent to the mouth, I'll just have to be satisfied with it for the time being.

GMRS is only licensable by individuals, period. An individual's "family" does not extend to anyone outside even that generously defined extended family.

I took a drive around this afternoon and found that the repeater's performance is pretty much the same using the 10' lower Workman antenna as the 10' higher Comet and the expensive heliax. I am strongly suspecting that it's a duplexer issue *and* a really poor front end on the receiver. Another friend kept me company and provided feedback as I drove around in roughly a 10 to 13 mile radius in my 45 watt mobile. On the 'fringes' he reported my audio was lower, but still solidly readable. Tomorrow I'm going to pack up the repeater and get it ready to ship back for warranty service. I've got another "home-brew" repeater that no one seems to want to buy that I can set up while the Bridgecom goes on vacation.

That would be helpful... Two updates to the situation for today. I received an email from Ron K. at Bridgecom who said that if I ship the repeater back to them in Missouri, he'll replace the duplexer with a new one from their new vendor, and also check out the entire system again, under warranty of course. But first, last night I had another QSO with my friend WQVY669 from his work location near the intersection of Columbus Ave. and Indianapolis Blvd. This is about 4 airline miles from me. I could hear him faintly on the repeater, but not reliably. He said he was going to go to 462.550 simplex. On a whim I got up and wandered back into the front office/hamshack and dialed that into my TYT TH-7800 and tossed out a call. Imagine my surprise when I got his reply at absolutely full quieting, with a solid four of eight bars on my digital scale! So, there are now two possibilities that occur to me since the only differences are: 1. antenna/feedline 2. radio receiver The TH-7800 is connected to my "old" dual-band antenna at roughly the same height as my new Comet 70cm antenna. I have a new Workman dual-band antenna and coax up on a chimney mount and have now snaked that cable through the window and have it connected to the repeater (after having swept it first of course!). He'll be back at work late tonight and hopefully we can run some tests to compare the repeater's receiver with my TYT TH-7800's receiver.

Okay, heliax is now uncoiled and lying on the ground around the tree trunk, and running into my office window directly to the repeater's antenna port. Now all I need is for someone to be on the air to help me test! Using two HT's to monitor myself doesn't really work all that well.

I already checked the tuning on the duplexer with my new Rigol spectrum analyzer. See the photo in the first post. I'm fixing to go out and move the heliax to pass through the window sash, and will "uncoil" the heliax at the same time. This way I can remove any "choke" that the coiled loops might be causing.

Four loops ~3'. It seems I overestimated how much I'd need by about 12'... <sigh>

You would be welcome anytime! Please do let me know if you every need any help. BTW, I attended a meeting of the NSEA a few weeks ago in Glenview. Among others I met Marc Drazin, who told me he should have his two repeaters back on line at the Hancock building within the next few months. He has two antennas on the roof (not in the gallery windows). No wonder his 550 machine had such terrific coverage! He also volunteered to see if he could find me some vertical real estate here in NW Indiana.

Okay, you are much closer to the mark than I was. I did however step across the street to take another photo with much less parallax. I also note that I misremembered the length of the antenna. It is actually 3.2m or 10.5' high... Measuring from the top of the rain gutter to the ground is precisely 11' 4". As you can see, when I stack three lines 11' 4" on top of one another, I can calculate ~34' to the tip of the antenna, which is 24' to the base, or 29' to the center point of the antenna. http://puu.sh/orOSE.jpg Obviously your range plot is much closer to reality and my own non-scientific range testing results. None of this of course has anything to do with the desensing issue. I posted the same info at radioreference.com and predictably several people have simply said "ditch that Comet" because it's a "hammy antenna." Er, since when was an antenna tuned for 460-470 MHz in the ham band? I'm willing to admit that it probably was a poor choice, but I can't afford a Decibel 8 bay Omni, nor would my roof tripod and mast support such a monster!

The duplexer is one that Bridgecom installed when building out my repeater. It is a Cellwave mobile duplexer with BNC connectors. Ron Kochanowicz (owner/engineer) replied this morning that "...when I tested your box with a service monitor, I was getting solid decode down to less than 0.25 uV with duplexer installed." He further clarified that this was an iso-T test. Nonetheless, even he suspects a duplexer desense problem. Not seen in the photos is this one showing about 10' of excess heliax. I can easily re-route the heliax through the lower sash of the window and connect it directly to the repeater to eliminate the lighting protector and the 6' RG213 jumper: http://puu.sh/orJSo.jpg

Corey, my mobile coverage is roughly 13 miles with 70% receiving the repeater, but only about 8 miles for transmitting to the repeater for 70% quieting. If it doesn't rain tomorrow, I'm going to try using dual antennas and by-pass the duplexer entirely. I will use the Comet for receive, and another antenna about 10' lower and physically 42' apart from the Comet. That should be plenty of separation.

Latitude 41.62674593 Longitude -87.51556871 The terrain around me is relatively flat for at least a 20 mile radius. FWIW, I had a long QSO with a friend who's currently at work. His 4watt HT connected to a roof mounted mag mount 1/4 wave was about 40% quieting with a lot of 'hash' in his audio. During the QSO I switched to 'base mode' on the repeater and his signal improved to at least 95% full quieting with only a soft "hiss" on the audio. This begins to smell like a de-sense issue with the duplexer. From the https://www.fcc.gov/media/radio/haat-calculator My average HAAT is 20.3m, or 66.6' |41|37|36.28|N|87|30|56.05|W|NAD 27| |202.0 meters RCAMSL| |20.3 meters Calculated HAAT| |NGDC/FCC Continental USA| | 0.0| 22.0| | 1.0| 22.0| | 2.0| 22.0| | 3.0| 22.0| | 4.0| 22.0| | 5.0| 22.0| | 6.0| 22.0| | 7.0| 22.0| | 8.0| 22.0| | 9.0| 22.0| | 10.0| 22.0| | 11.0| 22.0| | 12.0| 22.0| | 13.0| 22.0| | 14.0| 22.0| | 15.0| 22.0| | 16.0| 22.0| | 17.0| 22.0| | 18.0| 22.0| | 19.0| 22.0| | 20.0| 22.0| | 21.0| 22.0| | 22.0| 22.0| | 23.0| 22.0| | 24.0| 22.0| | 25.0| 22.0| | 26.0| 22.0| | 27.0| 22.0| | 28.0| 22.0| | 29.0| 22.0| | 30.0| 22.0| | 31.0| 22.0| | 32.0| 22.0| | 33.0| 22.0| | 34.0| 22.0| | 35.0| 22.0| | 36.0| 22.0| | 37.0| 22.0| | 38.0| 22.0| | 39.0| 22.0| | 40.0| 22.0| | 41.0| 22.0| | 42.0| 22.0| | 43.0| 22.0| | 44.0| 22.0| | 45.0| 22.0| | 46.0| 22.0| | 47.0| 22.0| | 48.0| 22.0| | 49.0| 22.0| | 50.0| 22.0| | 51.0| 22.0| | 52.0| 22.0| | 53.0| 22.0| | 54.0| 22.0| | 55.0| 22.0| | 56.0| 22.0| | 57.0| 22.0| | 58.0| 22.0| | 59.0| 22.0| | 60.0| 22.0| | 61.0| 22.0| | 62.0| 22.0| | 63.0| 22.0| | 64.0| 22.0| | 65.0| 22.0| | 66.0| 22.0| | 67.0| 22.0| | 68.0| 22.0| | 69.0| 22.0| | 70.0| 22.0| | 71.0| 22.0| | 72.0| 22.0| | 73.0| 22.0| | 74.0| 22.0| | 75.0| 22.0| | 76.0| 22.0| | 77.0| 22.0| | 78.0| 22.0| | 79.0| 22.0| | 80.0| 22.0| | 81.0| 22.0| | 82.0| 22.0| | 83.0| 22.0| | 84.0| 22.0| | 85.0| 22.0| | 86.0| 22.0| | 87.0| 22.0| | 88.0| 22.0| | 89.0| 22.0| | 90.0| 22.0| | 91.0| 22.0| | 92.0| 22.0| | 93.0| 22.0| | 94.0| 22.0| | 95.0| 22.0| | 96.0| 22.0| | 97.0| 22.0| | 98.0| 22.0| | 99.0| 22.0| |100.0| 22.0| |101.0| 22.0| |102.0| 22.0| |103.0| 22.0| |104.0| 22.0| |105.0| 22.0| |106.0| 22.0| |107.0| 22.0| |108.0| 22.0| |109.0| 22.0| |110.0| 22.0| |111.0| 22.0| |112.0| 22.0| |113.0| 22.0| |114.0| 22.0| |115.0| 22.0| |116.0| 22.0| |117.0| 22.0| |118.0| 22.0| |119.0| 22.0| |120.0| 22.0| |121.0| 22.0| |122.0| 22.0| |123.0| 21.9| |124.0| 21.8| |125.0| 21.6| |126.0| 21.3| |127.0| 21.0| |128.0| 20.7| |129.0| 20.5| |130.0| 20.3| |131.0| 20.2| |132.0| 20.2| |133.0| 20.3| |134.0| 20.1| |135.0| 19.8| |136.0| 19.4| |137.0| 19.1| |138.0| 18.9| |139.0| 18.9| |140.0| 19.0| |141.0| 19.2| |142.0| 19.4| |143.0| 19.6| |144.0| 19.6| |145.0| 19.3| |146.0| 19.0| |147.0| 19.0| |148.0| 19.1| |149.0| 19.0| |150.0| 18.6| |151.0| 18.0| |152.0| 17.5| |153.0| 17.2| |154.0| 16.9| |155.0| 16.8| |156.0| 16.9| |157.0| 17.0| |158.0| 17.0| |159.0| 17.1| |160.0| 17.3| |161.0| 17.3| |162.0| 17.3| |163.0| 17.0| |164.0| 16.6| |165.0| 16.2| |166.0| 15.9| |167.0| 15.8| |168.0| 15.8| |169.0| 15.9| |170.0| 16.1| |171.0| 16.4| |172.0| 16.7| |173.0| 16.6| |174.0| 16.3| |175.0| 16.0| |176.0| 16.2| |177.0| 16.4| |178.0| 16.4| |179.0| 16.2| |180.0| 16.0| |181.0| 15.9| |182.0| 15.9| |183.0| 16.0| |184.0| 16.0| |185.0| 16.0| |186.0| 16.1| |187.0| 16.1| |188.0| 16.0| |189.0| 15.9| |190.0| 16.1| |191.0| 16.3| |192.0| 16.5| |193.0| 16.3| |194.0| 16.3| |195.0| 16.4| |196.0| 16.7| |197.0| 17.1| |198.0| 17.4| |199.0| 17.6| |200.0| 17.6| |201.0| 17.5| |202.0| 17.4| |203.0| 17.3| |204.0| 17.0| |205.0| 16.9| |206.0| 16.8| |207.0| 16.8| |208.0| 16.9| |209.0| 17.0| |210.0| 17.2| |211.0| 17.4| |212.0| 17.6| |213.0| 17.8| |214.0| 18.1| |215.0| 18.3| |216.0| 18.5| |217.0| 18.6| |218.0| 18.6| |219.0| 18.7| |220.0| 19.0| |221.0| 19.2| |222.0| 19.1| |223.0| 19.1| |224.0| 19.2| |225.0| 19.4| |226.0| 19.4| |227.0| 19.2| |228.0| 19.0| |229.0| 18.9| |230.0| 18.6| |231.0| 18.0| |232.0| 17.3| |233.0| 16.7| |234.0| 16.1| |235.0| 15.7| |236.0| 15.4| |237.0| 15.3| |238.0| 15.4| |239.0| 15.5| |240.0| 15.5| |241.0| 15.7| |242.0| 16.1| |243.0| 16.6| |244.0| 17.2| |245.0| 18.0| |246.0| 18.6| |247.0| 19.0| |248.0| 19.0| |249.0| 19.0| |250.0| 19.2| |251.0| 19.5| |252.0| 19.8| |253.0| 20.0| |254.0| 20.2| |255.0| 20.3| |256.0| 20.6| |257.0| 20.9| |258.0| 21.1| |259.0| 21.3| |260.0| 21.4| |261.0| 21.5| |262.0| 21.6| |263.0| 21.7| |264.0| 21.8| |265.0| 21.9| |266.0| 22.0| |267.0| 22.0| |268.0| 22.0| |269.0| 22.0| |270.0| 22.0| |271.0| 22.0| |272.0| 22.0| |273.0| 22.0| |274.0| 22.0| |275.0| 22.0| |276.0| 22.0| |277.0| 22.0| |278.0| 22.0| |279.0| 22.0| |280.0| 22.0| |281.0| 22.0| |282.0| 22.0| |283.0| 22.0| |284.0| 22.0| |285.0| 22.0| |286.0| 22.0| |287.0| 22.0| |288.0| 21.9| |289.0| 21.7| |290.0| 21.1| |291.0| 20.5| |292.0| 20.0| |293.0| 19.8| |294.0| 19.7| |295.0| 19.5| |296.0| 19.3| |297.0| 19.0| |298.0| 18.8| |299.0| 18.5| |300.0| 18.2| |301.0| 17.9| |302.0| 17.7| |303.0| 17.7| |304.0| 17.8| |305.0| 18.1| |306.0| 18.6| |307.0| 19.2| |308.0| 19.9| |309.0| 20.4| |310.0| 20.9| |311.0| 21.4| |312.0| 21.7| |313.0| 22.0| |314.0| 22.0| |315.0| 22.0| |316.0| 22.0| |317.0| 22.0| |318.0| 22.0| |319.0| 22.0| |320.0| 22.0| |321.0| 22.0| |322.0| 22.0| |323.0| 22.0| |324.0| 22.0| |325.0| 22.0| |326.0| 22.0| |327.0| 22.0| |328.0| 22.0| |329.0| 22.0| |330.0| 22.0| |331.0| 22.0| |332.0| 22.0| |333.0| 22.0| |334.0| 22.0| |335.0| 22.0| |336.0| 22.0| |337.0| 22.0| |338.0| 22.0| |339.0| 22.0| |340.0| 22.0| |341.0| 22.0| |342.0| 22.0| |343.0| 22.0| |344.0| 22.0| |345.0| 22.0| |346.0| 22.0| |347.0| 22.0| |348.0| 22.0| |349.0| 22.0| |350.0| 22.0| |351.0| 22.0| |352.0| 22.0| |353.0| 22.0| |354.0| 22.0| |355.0| 22.0| |356.0| 22.0| |357.0| 22.0| |358.0| 22.0| |359.0| 22.0|

I have been having some poor receive sensitivity with my new Bridgecom repeater system, and I'm trying to narrow down just where I might take some action to improve things. Beginning with the antenna system seems a good place to start. The antenna is a monoband Comet CA-712EFC mounted on a roof tripod on a 10' mast. With the combined height of the roof the base of the 8' antenna is at 52' AGL. The feedline is 60' of new 1/2" Comscope heliax, which terminates in a new MFJ-270 Lightning Surge Protector (Gas) just outside my office/shack exterior wall. It is brought into the repeater with 6' of RG-213. I've done a sweep of the entire antenna system with a Surecom SA-250 Antenna Analyzer. The lowest SWR is 1.09 @ 461.275 MHz. At the receive frequency of 467.675 MHz the SWR is 1.32 (see details in next image) : http://puu.sh/or8Lw.jpg Averages on a single frequency, 10 pass sweep are shown in the next image. The camera didn't focus too well for this image, but it should still be readable. SWR 1.32 Zx 50.1 ohms Rs 57.5 jX -28 http://puu.sh/or9sa.jpg The final image is at the transmit frequency of 462.675 MHz. This image is crystal clear so I won't transcribe the results. I cannot spot anything that stands out as a possible problem. http://puu.sh/or9Kn.jpg The last image is a composite trace of the duplexer. Note that the insertion loss at the receive frequency is -1.42 dB, which isn't all that bad! The reject of the transmit frequency isn't all that spectacular, but should be acceptable at -70.81 dB. http://puu.sh/ora4W.png The transmitter is limited to 20 watts output in an attempt to better balance the system. It is capable of a full 50 watts continuous duty. Range testing with a 4 watt Motorola XPR7550 shows full quieting at 1 mile, 70% quieting at 2 miles, but unreadable at 3 miles. With the antenna height and average 5' portable/mobile height, I should be seeing around 10 miles for 70% HT coverage by my calculations. Does anyone have any suggestions as to where next to look?