- Noisy repeater output - 5 Updates
| Eremita Analogico <LEDITApaolo.carrer@DALNASOlibero.it>: Jun 13 08:27PM +0200 Hi, my old HT DMM is still abandoned, but... I must repair a Vertex VRX-7000 repeater that has a noisy output: https://i.postimg.cc/3JhhbHpC/IMG-3321-1.jpg Do you know how can generate this noise, also UNDER the trasmitting frequency? The receiver frequency falls in the noisy area, and when I connect a duplexer, the sensitivity of receiver is blanked. I still must begin to investigate, but if someone know something, I will much appreciate any suggestion. Thanks. |
| Ralph Mowery <rmowery28146@earthlink.net>: Jun 13 04:04PM -0400 In article <qdu4j9$3ok$1@gioia.aioe.org>, LEDITApaolo.carrer@DALNASOlibero.it says... > frequency? > The receiver frequency falls in the noisy area, and when I connect a > duplexer, the sensitivity of receiver is blanked. Go here and ask the question , Many repeater owners are here. https://groups.io/g/repeater-builder It could normal for the transmiter. How many notch cavities are you using for a duplexer > |
| Jeff Liebermann <jeffl@cruzio.com>: Jun 13 08:09PM -0700 On Thu, 13 Jun 2019 20:27:52 +0200, Eremita Analogico >Hi, my old HT DMM is still abandoned, but... >I must repair a Vertex VRX-7000 repeater that has a noisy output: >https://i.postimg.cc/3JhhbHpC/IMG-3321-1.jpg Argh. You're overdriving the spectrum analyzer. Most of the junk looks like it's coming from intermod mixing between the harmonics produced in the now non-linear spectrum analyzer input states. The SA shows that your input signal is 4.52dBm (about 3mw) into an internal 10dB attenuator. What model HP spectrum analyzer are you using and will it tolerate a +5dBm input signal level? Put some external -10dB attenuators in line and see if the junk (noise) decreases. If it decreases more than -10dB, then it's being generated in the SA by your overload. If it drops exactly -10DB, then it's real. >frequency? >The receiver frequency falls in the noisy area, and when I connect a >duplexer, the sensitivity of receiver is blanked. Duplexer tuning and cabling are somewhat of an art. For example, the coax cables between the duplexer and the receiver input, and between the duplexer and the transmitter output MUST be an odd multiple of 1/2 wavelength electrical long, as measured from the pickup loop in the cavities, to the receiver front end device or transmitter RF output transistor. Use the wrong length, or wrong connectors, and you'll never get the rated isolation. I agree with Ralph Mowery. Go to: <https://groups.io/g/repeater-builder> and ask the same question, but also include what radio and duplexer you are using. Also what test equipment you have available. Most important, exactly what problem you are trying to solve that required troubleshooting. >I still must begin to investigate, but if someone know something, I will >much appreciate any suggestion. There a many articles and videos on the web on "duplexer tuning". I would recommend one, but need to know the details of your repeater to find something appropriate. <https://www.google.com/search?q=duplexer+tuning> Good luck. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
| Eremita Analogico <LEDITApaolo.carrer@DALNASOlibero.it>: Jun 14 02:16PM +0200 Il 14/06/2019 05:09, Jeff Liebermann ha scritto: > Argh. You're overdriving the spectrum analyzer. Most of the junk > looks like it's coming from intermod mixing between the harmonics > produced in the now non-linear spectrum analyzer input states. I don't think so. The repeater TX has an output of 10W. Prior to enter in the spectrum analyzer, the signal is reduced by a 20 dB in line attenuator. > The SA shows that your input signal is 4.52dBm (about 3mw) into an > internal 10dB attenuator. What model HP spectrum analyzer are you > using and will it tolerate a +5dBm input signal level? The SA input tolerate 1W (30 dBm) The model is 8590B > cavities, to the receiver front end device or transmitter RF output > transistor. Use the wrong length, or wrong connectors, and you'll > never get the rated isolation. We have tryed with Procom and Motorola duplexers, both with 3 adjustable cavities for RX path and another 3 adjustable cavities for TX path. The same duplexers work perfectly with a repeater built with two separate Simoco SRM9000, without any desensization of RX unit when the TX is operated. Thus, I think that the PA of Vertex VRX7000 has some issues, but I never seen noises of that type. I wolud expect some harmonics. The internal supply can do this noise? > find something appropriate. > <https://www.google.com/search?q=duplexer+tuning> > Good luck. Ok, thanks, I will try also the repeater-builder forum, but if I can obtain some useful tips without register me I will much appreciate. Wednesday I will resume the repeater investigation. |
| Eremita Analogico <LEDITApaolo.carrer@DALNASOlibero.it>: Jun 14 02:16PM +0200 Il 13/06/2019 22:04, Ralph Mowery ha scritto: > https://groups.io/g/repeater-builder > It could normal for the transmiter. How many notch cavities are you > using for a duplexer > Thanks, please follow the answer to Jeff Liebermann |
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