|
Re: Isocoupler
Please be aware that using an Iso-coupler or installing any antenna on an AM tower can change the impedance of the tower and trigger the need for a proof, especially if you're doing this on a tower that's part of a directional antenna system.? The Iso-coupler will add a shunt capacitance to the tower and the antenna can also change the base impedance and current distribution of a tower.??
An ISO-coil can add a shunt inductance and may need a parallel capacitor to detune it at the stations operating frequency. Be careful when fooling with AM towers. Burt, K6OQK |
|
Re: QUANTAR VHF Audio Interface...
Chris,
I will not disagree with you, but it's just that you and I have different approaches to the on-going problems of audio levels of repeater users. I consider the W6MEP repeater a repeater for all users, not just those that have the technical ability and knowledge to adjust mic gain and deviation, or speak from the diaphragm and always use proper mic technique. Not to put anyone down, but trying to get users to correct audio issues can be a fruitless adventure. I choose to take care of the problem on my end, where I have the ability to do something about it and sleep at night. Besides, it makes for a better "user experience" and the user doesn't have to put up with me nagging on them to fix their audio problems. I will agree that a lot of the so called "processors" built in to some radios are junk. Don't base all processing on the junk ones. I've played with some of those radios, and most recently, the so called processing in a QUANTAR. It essentially just drives the masher a little harder and, in my opinion, makes for unpleasant sounding audio. I recently ran a stock QUANTAR for W6MEP for a little over a week and didn't care for the sound of it. Some users said it sounded fine, many complained. A lot of the opinions are based on the sound quality of the users receiver.? As they sometimes say in broadcasting, "The stations only sounds as good as the engineer's radio." Obtaining an older FM Optimod, such as the 8100A, is really not that difficult, especially if you're in the technical side of broadcasting like you and I. So many stations have upgraded to the latest Belch-Fire 7+ processors and have relegated their older (but excellent) Optimod 8100A's to the back shelf. Speak to them, it won't hurt to ask. Please, don't think for a moment that I had the money to spend for one, although I did re-cap and proof the one I'm using. Burt, K6OQK *** Nov 5 ? #195383??
Well, an 8100 is nice, especially with the XT chassis lol, but not everybody can afford an Optimod or Orban audio processor..... I have a 6300 but it's for sale... Kind of overkill for ham radio and my FM translator fell through so what the heck. My feeling is if somebody has a problem with their audio THEY need to fix it, not the repeater.... in my book, a repeater should do nothing to a user's audio except pass it as is. When I got my RC850, the first thing I did was pull out the AGC that was in there because I felt it was pumping the audio too much. And I never looked back.
|
|
Re: QUANTAR VHF Audio Interface...
Well,? an 8100 is nice, especially with the XT chassis lol,? but not everybody can afford an Optimod or Orban audio processor..... I have a 6300 but it's for sale... Kind of overkill for ham radio and my FM translator fell through so what the heck. My feeling is if somebody has a problem with their audio THEY need to fix it, not the repeater.... in my book, a repeater should do nothing to a user's audio except pass it as is. When I got my RC850, the first thing I did was pull out the AGC that was in there because I felt it was pumping the audio too much. And I never looked back. On Sat, Nov 5, 2022, 9:19 PM nj902 <nj0907@...> wrote: Burt, |
|
Re: QUANTAR VHF Audio Interface...
Gang,
Please understand, my intention to transmit what has been refereed to as wideband audio is not to be HiFi, but to be something better than typical "telephone quality" audio.? I do not feel that I'm a part of the "government" where I can simply repeal the Laws of Physics that don't suit my needs - although I've tried. For occupied bandwidth measurements I use an Anritsu MS2721B spectrum analyzer.? I set the span to 100 kHz, the RBW (Resolution Bandwidth) to 100 Hz, and VBW (Video Bandwidth) to 30 kHz, and also use peak store.? With the repeater in use that has a mix of fully quieting and noisy signals I let the analyzer sweep for 10 minutes or longer.? It's best if I make these measurements at the sample out of the transmitter, but I can get a fairly good representation of reality from home. W6MEP runs 4 to 4.2 kHz peak deviation.? In the next few days I will post some spectrographs of the W6MEP repeater's occupied bandwidth.? In the meantime, I invite anyone in the range of the repeater to make occupied bandwidth measurements and show me where we are exceeding the limits imposed by good engineering, TASMA or any other coordinating group.? We do have a system that operates with its output 15 kHz below us and due to a deviation misadjustment on my part they were justifiably complaining about some interference.? Since I corrected the deviation they have not complained. So, what am I using for processing?? I'm using an ORBAN 8100A, an FM broadcast processor.? A few people have gotten up in arms over this, so yes, this is a stereo processor with a stereo generator in it.? I have the stereo generator disabled which kills the stereo pilot and L-R sub channel.? It provides the following: Audio AGC, peak limiting, a protection peak limiter,(not clipping) and pre-emphasis.? Granted, the pre-emphasis is 75 usec, not the typical communications whatever pre-emphasis.? It's essentially flat from 50 Hz to 1 kHz and then begins a 6dB/Octave pre-emphasis boost above 1 kHz.? Between the processor output and the Direct FM Varactor modulator of the transmitter I have a 5 kHz low pass filter that's pretty steep.? Here's an important factor to be aware of: the limiter and protection limiter are "pre-emphasis aware."? This means that it anticipates pre-emphasized modulating frequency verses deviation and, for lack of a better way to put it, it keeps the deviation from climbing at higher frequencies.? On noisy signals, squelch tails, or just plain blowing squelch, it holds the deviation to set parameters. The audio AGC has a fairly fast attack, which is adjustable, and a fairly slow release, which is also adjustable. What the AGC doesn't catch on attack, the limiter portion will catch. It's also gated, which means that when a quieting station stops talking, the AGC release stops and remains where it stopped until audio returns. A lot of us Hams speak right up in one sentence and then mumble in the next. Set up this way you don't hear it pumping up audio between words, sentences or other pauses in speech.? On noisy signals it's barely noticeable. One of the things about having the 75 usec preempahsis is that it allows the low end to be there.? It's not pushed or boosted, but it's not lost. The W6MEP repeater sounds clean and what comes in is what comes out, with the exception that the audio level is pretty consistent, even when screaming or mumbling in the mic. There are some that disagree, telling me I'm bringing up the noise when the audio expands.? Well, yes, but to hear someone that's only deviation a half kHz into a repeater, you have to turn up the audio if you want to hear them, and in doing so you're turning up not only any noise coming in to the repeater, but any noise between you and the repeater - Is that any better?? I get a lot of compliments on the fact that the W6MEP is easy to listen to; users don't have to turn the audio up and down, and it's clean sounding. I hope the above epistle gives a little insight into how the W6MEP repeater audio is controlled. There will be more. Burt, K6OQK nj902 Nov 4 ? #195367??
Burt's intention to transmit wideband audio in the interest of increased clarity or voice 'fidelity' prompted several people to express concern about the resulting signal bandwidth - especially on 2 meters in locations with 15 kHz channel spacing.
?
Burt replied: "I do regularly monitor my occupied bandwidth"
?
This is an excellent topic.? Burt, In the interest of sharing your knowledge and expertise with less experienced members of the group, could you provide a description of the process you use, equipment required,?and how to interpret the results in the context of not interfering with adjacent channel operations.? It would also be helpful if you could post an image or two... |
|
Re: VHF MTR2000 Poor Receive Performance
¿ªÔÆÌåÓýOkay-
From the graph - I'd guess the directional coupler is a -20dB model.? And - it looks like you're getting the expected directivity and RL trace that I would have expected - considering I don't know quality of the load of the exact value of the DC. As such - and from your other graphs of a different post, it would seem your receiver isn't tuned properly.? And if it is - it has terrible return loss at the desired receive frequency.? Enough so that notch depths are probably being degraded - to some degree.? Kevin On 11/5/2022 12:26 PM, Jared Smudde wrote: Here you go. |
Burt K6OQK
WB6HRO
Karl Shoemaker
Chris Boone WB5ITT
Jared Smudde
Kevin Custer
