Re: [Repeater-Builder] Re: Ok, here's a weird one....
If you are going to leave the long end open and still have a problem a .001 cap to ground often will solve it From: Nate Duehr [EMAIL PROTECTED] Reply-To: Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Ok, here's a weird one Date: Wed, 14 Feb 2007 21:10:28 -0700 On 2/14/07, Eric Lemmon [EMAIL PROTECTED] wrote: And, in most cases, the cable shield should be grounded only on the receiving end, to minimize noise pickup. 73, Eric Lemmon WB6FLY Now that's a trick I wasn't aware of, but it makes intuitive sense. Thanks Eric. Nate WY0X _ Advertisement: Fresh jobs daily. Stop waiting for the newspaper. Search Now! www.seek.com.au http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fninemsn%2Eseek%2Ecom%2Eau_t=757263760_r=Hotmail_EndText_Dec06_m=EXT
[Repeater-Builder] Re: Ok, here's a weird one....
--- In Repeater-Builder@yahoogroups.com, Ken Arck [EMAIL PROTECTED] wrote: Have a customer with the following issue: Scenario: Amateur repeater (Mastr II) installed at a 100,000 FM radio xmtr site. Issue: Very low level audio of radio station appears on Mastr II's xmtr (yes, external controller). Repeater owner hasn't fully explained what very low level means. But regardless. Question: The only way I see this happening is due to some AM component on radio station's transmitter. Thoughts? Thoughts? I haven't seen it mentioned yet, but yes, this sounds like a classic case of Intermood. The repeater antenna and feed line are passive items, meaning that they don't do anything but sit there with the ability to transmit and receive on different frequencies at the same time! The FM station's 100KW signal comes into the repeater's coax from the antenna, mixes in the repeater's finale which is a nonlinear class C circuit, and gets transmitted on the repeater's output. IF this is the case, a cavity filter tuned to the FM station's signal, at the botom of the coax at the repeater's output, should take out the offending signal. This can be built out of a large tin can, per data on the Internet. Suggest starting with 2 number 10 tin cans stacked and soldered together for that frequency, which would be bigger than one number 10 cavity, made for 2 meters or above. Also to consider, having a 100KW FM broadcast signal right next to a antenna, coax, and repeater receiver rated in the microvolt region, is a lot to expect, overloading the receiver and probably also causing desence in the repeater receiver. A cavity at the repeater receiver, also tuned to the 100KW FM station's carrier, should solve that. Been there, done that! Best wishes, Dick, W7TIO (retired Mobile Radio Communications tech.) Ken --- --- President and CTO - Arcom Communications Makers of the world famous RC210 Repeater Controller and accessories. http://www.arcomcontrollers.com/ Authorized Dealers for Kenwood and Telewave and we offer complete repeater packages! AH6LE/R - IRLP Node 3000 http://www.irlp.net
[Repeater-Builder] Re: Ok, here's a weird one....
I haven't seen it mentioned yet, but yes, this sounds like a classic case of Intermood. I don't think it is classic intermod. Think about it. The deviation of the broadcast station is 75 kc. A signal that wide cannot be heard in a receiver designed for 5 kc., except, maybe, VERY distorted, and even then, the squelch circuit usually will not open with such a signal present. I've dealt with FM broadcast intermod on a repeater that I maintain. This one is the classic A+B-C formula. 89.9 + 147.06 - 89.3 = 147.66. Yes, this produces a signal on our 7.66 input, but is VERY wide. It does not manifest itself until, and only until, both broadcast stations have no modulation on them at the same time. Only then does the intermod product become narrow enough to stay within the passband of our receiver and be heard. The instant either broadcast station begins modulating, our squelch closes, and the intermod is not heard. I've traced the mixing to the tower guy wire anchor area. Tower riggers weave cable through the turnbuckles. This creates numerous places where metal is barely touching and rubbing, a great place for mini-diodes and just plain scratching noise too. Placing sections of vinyl insulation in problem areas cures the problem here. Best wishes, Dick, W7TIO (retired Mobile Radio Communications tech.) Ken Laryn K8TVZ
Re: [Repeater-Builder] Re: Ok, here's a weird one....
Umm.. what he said. With another twist or two... Heretofore, it's been assumed the culprit to be main channel RF, because they're hearing main-channel audio... You'll want to consider what *other* things may be going on ~~ * STL (studio-transmitter-link) channels ~ typically in the 950 range, but not always * RPU/IFB channels ~ which generally aren't wide-band, and have been known to run continuously. Laryn Lohman wrote: I haven't seen it mentioned yet, but yes, this sounds like a classic case of Intermood. I don't think it is classic intermod. Think about it. The deviation of the broadcast station is 75 kc. snip.
RE: [Repeater-Builder] Re: Ok, here's a weird one....
Dennis, I have the same problem also. Did you place the filter between the antenna and duplexer? I have mine installed between the RX and Duplexer. Depending the WX I can hear the FM Station on my two meter repeater, but thought the RF was getting into the cables, etc. I may have to switch the location of my filter. Thanks JIM KA2AJH _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of numberone5call Sent: Tuesday, February 13, 2007 9:26 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Ok, here's a weird one Ken; I can only tell you what worked for myself and a friend w another repeater. Both repeaters were/are located on hi-power FM broadcast towers. Both FM broadcast radio transmissions cud barely be heard on the outputs of the repeaters (only when the rptrs were tx'n, under the tx audio). Both cases a dci bandpass filter eliminated the rebroadcast of the FM stations. This are both 2mtr repeaters. Hope this helps!!! Dennis no5c 146.970 no5c/R pl100hz 444.500 w5LRG/R Lauderdale Repeater Group w5LRG Meridian, MS --- In Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com, Ken Arck [EMAIL PROTECTED] wrote: Have a customer with the following issue: Scenario: Amateur repeater (Mastr II) installed at a 100,000 FM radio xmtr site. Issue: Very low level audio of radio station appears on Mastr II's xmtr (yes, external controller). Repeater owner hasn't fully explained what very low level means. But regardless. Question: The only way I see this happening is due to some AM component on radio station's transmitter. Thoughts? Ken -- --- President and CTO - Arcom Communications Makers of the world famous RC210 Repeater Controller and accessories. http://www.arcomcon http://www.arcomcontrollers.com/ trollers.com/ Authorized Dealers for Kenwood and Telewave and we offer complete repeater packages! AH6LE/R - IRLP Node 3000 http://www.irlp. http://www.irlp.net net
[Repeater-Builder] Re: Ok, here's a weird one....
It was mounted flat to the IFAS board using the provided double sided tape. And yes the cover was on the station shelf. Steve - Original Message - From: Fred Flowers To: Repeater-Builder@yahoogroups.com Where did you have the TS-64's mounted? Fred N4GER
Re: [Repeater-Builder] Re: Ok, here's a weird one....
Oops, brain fart, I meant to say it was mounted to the system board. - Original Message - From: Steve Subject: [Repeater-Builder] Re: Ok, here's a weird one It was mounted flat to the IFAS board using the provided double sided tape. And yes the cover was on the station shelf. Steve - Original Message - From: Fred Flowers To: Repeater-Builder@yahoogroups.com Where did you have the TS-64's mounted? Fred N4GER
RE: [Repeater-Builder] Re: Ok, here's a weird one....
I was wondering how you did that. -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Steve Sent: Wednesday, February 14, 2007 4:15 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Ok, here's a weird one Oops, brain fart, I meant to say it was mounted to the system board. - Original Message - From: Steve Subject: [Repeater-Builder] Re: Ok, here's a weird one It was mounted flat to the IFAS board using the provided double sided tape. And yes the cover was on the station shelf. Steve - Original Message - From: Fred Flowers To: Repeater-Builder@yahoogroups.com Where did you have the TS-64's mounted? Fred N4GER Yahoo! Groups Links
[Repeater-Builder] Re: Ok, here's a weird one....
--- In Repeater-Builder@yahoogroups.com, Nate Duehr [EMAIL PROTECTED] wrote: with all the grounds checked to be tied only to ONE end (ground loops are evil beasts), cleared up the problem... no more new Country in the background lightly. Nate WY0X That's right, most people ground both ends of shielded audio cable. You should probably be using a shielded pair, with the pair being the audio circuit, and shield around the pair grounded at only ONE end. The goal is to not have any current flowing in the shield. Shields are often handled this way in radio stations and other pro audio applications. Laryn K8TVZ
RE: [Repeater-Builder] Re: Ok, here's a weird one....
And, in most cases, the cable shield should be grounded only on the receiving end, to minimize noise pickup. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Laryn Lohman Sent: Wednesday, February 14, 2007 5:38 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Ok, here's a weird one --- In Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com , Nate Duehr [EMAIL PROTECTED] wrote: with all the grounds checked to be tied only to ONE end (ground loops are evil beasts), cleared up the problem... no more new Country in the background lightly. Nate WY0X That's right, most people ground both ends of shielded audio cable. You should probably be using a shielded pair, with the pair being the audio circuit, and shield around the pair grounded at only ONE end. The goal is to not have any current flowing in the shield. Shields are often handled this way in radio stations and other pro audio applications. Laryn K8TVZ
[Repeater-Builder] Re: Ok, here's a weird one....
If i'm not mistaken It was put between the duplexer and the antenna. The site I used i no longer use. The friend still uses his site and the dci filter i loaned him is still in line and doing the job. I think he also uses it between the duplexer and antenna. Dennis no5c --- In Repeater-Builder@yahoogroups.com, Jim Cicirello [EMAIL PROTECTED] wrote: Dennis, I have the same problem also. Did you place the filter between the antenna and duplexer? I have mine installed between the RX and Duplexer. Depending the WX I can hear the FM Station on my two meter repeater, but thought the RF was getting into the cables, etc. I may have to switch the location of my filter. Thanks JIM KA2AJH _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of numberone5call Sent: Tuesday, February 13, 2007 9:26 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Ok, here's a weird one Ken; I can only tell you what worked for myself and a friend w another repeater. Both repeaters were/are located on hi-power FM broadcast towers. Both FM broadcast radio transmissions cud barely be heard on the outputs of the repeaters (only when the rptrs were tx'n, under the tx audio). Both cases a dci bandpass filter eliminated the rebroadcast of the FM stations. This are both 2mtr repeaters. Hope this helps!!! Dennis no5c 146.970 no5c/R pl100hz 444.500 w5LRG/R Lauderdale Repeater Group w5LRG Meridian, MS --- In Repeater-Builder@ mailto:Repeater-Builder% 40yahoogroups.com yahoogroups.com, Ken Arck ah6le@ wrote: Have a customer with the following issue: Scenario: Amateur repeater (Mastr II) installed at a 100,000 FM radio xmtr site. Issue: Very low level audio of radio station appears on Mastr II's xmtr (yes, external controller). Repeater owner hasn't fully explained what very low level means. But regardless. Question: The only way I see this happening is due to some AM component on radio station's transmitter. Thoughts? Ken -- --- President and CTO - Arcom Communications Makers of the world famous RC210 Repeater Controller and accessories. http://www.arcomcon http://www.arcomcontrollers.com/ trollers.com/ Authorized Dealers for Kenwood and Telewave and we offer complete repeater packages! AH6LE/R - IRLP Node 3000 http://www.irlp. http://www.irlp.net net
Re: [Repeater-Builder] Re: Ok, here's a weird one....
On 2/14/07, Eric Lemmon [EMAIL PROTECTED] wrote: And, in most cases, the cable shield should be grounded only on the receiving end, to minimize noise pickup. 73, Eric Lemmon WB6FLY Now that's a trick I wasn't aware of, but it makes intuitive sense. Thanks Eric. Nate WY0X
[Repeater-Builder] Re: Ok, here's a weird one....
At 10:09 AM 2/13/2007, Ken Arck wrote: Have a customer with the following issue: Scenario: Amateur repeater (Mastr II) installed at a 100,000 FM radio xmtr site. Make that 100,000 watt (at least the claim is 100K) Ken -- President and CTO - Arcom Communications Makers of the world famous RC210 Repeater Controller and accessories. http://www.arcomcontrollers.com/ Authorized Dealers for Kenwood and Telewave and we offer complete repeater packages! AH6LE/R - IRLP Node 3000 http://www.irlp.net
[Repeater-Builder] Re: Ok, here's a weird one....
--- In Repeater-Builder@yahoogroups.com, Ken Arck [EMAIL PROTECTED] wrote: Have a customer with the following issue: Scenario: Amateur repeater (Mastr II) installed at a 100,000 FM radio xmtr site. Issue: Very low level audio of radio station appears on Mastr II's xmtr (yes, external controller). Repeater owner hasn't fully explained what very low level means. But regardless. Question: The only way I see this happening is due to some AM component on radio station's transmitter. Thoughts? Ken A couple related cases: I had a problem with a 15kW FM station getting into the baseband of a nearby analog microwave radio. You could hear distorted peaks of the broadcast station audio low on the baseband. Removing all feed lines from the site entry plate one at a time revealed a noisy (but otherwise working) N elbow adapter on another radio. I recall a problem from another site where nearby mobiles on ch X would open up satellite receiver X plus several others on different channels. All these receivers had the same crystal clear audio from the mobile unit as if it were transmitting on all channels at once. This one turned out to be a bad preamp in a preselector shelf. My point would be that these types of problems with near-field RF mixing in who-knows-what can be and often are just about anything. Good luck! (You can always TRY liberal grounding and shielding.) James K7ICU
Re: [Repeater-Builder] Re: Ok, here's a weird one....
Hell, I could spend a week on top of a mountain with an Oscilloscope, Spectrum Analyzer and function generator and still not trace down what is actually happening. Survey says: Incidental AM from a weak tube in the FM tranmitter final stage coupling to DC power leads as an antenna and then being rectified with the polarity protection diodes and filter capacitors into AC and interfering with power supply of op-amp's VDD and VPP. Using a ferrite around the cables may help as well as placing the controller in a RF tight enclosure. Feed through capacitor DB-9s may be nessacary as well. Then if you are still getting the noise, it could be the carrier actually being rectified on the silicon inside the op-amps, in which case your screwed. Also not as likely but could happen, the site power is actually modulating with the FM transmitter and the repeater power supply is not able to filter it out. This can be proven by running the station on a battery and the audio goes away. On 2/13/07, Ken Arck [EMAIL PROTECTED] wrote: At 10:09 AM 2/13/2007, Ken Arck wrote: Have a customer with the following issue: Scenario: Amateur repeater (Mastr II) installed at a 100,000 FM radio xmtr site. Make that 100,000 watt (at least the claim is 100K) Ken -- President and CTO - Arcom Communications Makers of the world famous RC210 Repeater Controller and accessories. http://www.arcomcontrollers.com/ Authorized Dealers for Kenwood and Telewave and we offer complete repeater packages! AH6LE/R - IRLP Node 3000 http://www.irlp.net Yahoo! Groups Links
[Repeater-Builder] Re: Ok, here's a weird one....
Ken; I can only tell you what worked for myself and a friend w another repeater. Both repeaters were/are located on hi-power FM broadcast towers. Both FM broadcast radio transmissions cud barely be heard on the outputs of the repeaters (only when the rptrs were tx'n, under the tx audio). Both cases a dci bandpass filter eliminated the rebroadcast of the FM stations. This are both 2mtr repeaters. Hope this helps!!! Dennis no5c 146.970 no5c/R pl100hz 444.500 w5LRG/R Lauderdale Repeater Group w5LRG Meridian, MS --- In Repeater-Builder@yahoogroups.com, Ken Arck [EMAIL PROTECTED] wrote: Have a customer with the following issue: Scenario: Amateur repeater (Mastr II) installed at a 100,000 FM radio xmtr site. Issue: Very low level audio of radio station appears on Mastr II's xmtr (yes, external controller). Repeater owner hasn't fully explained what very low level means. But regardless. Question: The only way I see this happening is due to some AM component on radio station's transmitter. Thoughts? Ken --- --- President and CTO - Arcom Communications Makers of the world famous RC210 Repeater Controller and accessories. http://www.arcomcontrollers.com/ Authorized Dealers for Kenwood and Telewave and we offer complete repeater packages! AH6LE/R - IRLP Node 3000 http://www.irlp.net
