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#1
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best architecture for a homebrewed single-station FM broadcast dx receiver?
a city I visit frequently -or more precisely, it's exurban outskirts -
has only one mellow-Jazz FM-broadcast station, the only one for many hundreds of miles. thus I have decided to build my own single-station hi-performance receiver to get the one station. I know enough to know that ideally, the bulk of the gain, directionality, selectivity should be at the antenna itself. Or even more to the point, tower height. At least ideally. And hi-performance single FM channel yagi's are easily spec'd from a number of antenna houses. So that issue is not being placed on this table. The rest of the gain budget is. Let the discussions begin. For example, what approach do the known "name" receivers (Kloss Model One, GE Super Radio) use? can a homebrewer do better? Which commercial house builds the best resonant chambers for the 108 Mhz frequency? Can be be done easily at home? how about the demodulation and audio portions? |
#2
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Building a good receiver of any kind is complex, if you really want
good specs. Very few people have been able to accomplish this at home. Just for calibration, you will require the proper instruments and skills. A good FM receiver with the proper antenna will do it, as long as the antenna can see over the horizon, and within your distance range there are no other stations at the same frequency. There are also the physical limitations to consider as well. Since the range of an FM station is about 120 to 140 miles at the very best with a good antenna, there may be allowance for other stations to broadcast within a 150 mile radius. If there are other stations, these may be difficult to tune out. You would be best off with an antenna that is cut to the frequency you want to recieve, it will have to be able to see over the horizon enough to see the transmitter site, have the proper directivity, and be very well impedance matched to the receiver. All the high end FM tuners are designed to be able to use an external antenna, using a 75 ohm coax type hookup. Have you considered calling this station to see if they are on the net, satellite service, or on your local cable TV service? Many of these small stations are on the net, and broadcast streamed programming. This way you can use your computer to listen to them. ' Jerry Greenberg -- (Alan Horowitz) wrote in message ... a city I visit frequently -or more precisely, it's exurban outskirts - has only one mellow-Jazz FM-broadcast station, the only one for many hundreds of miles. thus I have decided to build my own single-station hi-performance receiver to get the one station. I know enough to know that ideally, the bulk of the gain, directionality, selectivity should be at the antenna itself. Or even more to the point, tower height. At least ideally. And hi-performance single FM channel yagi's are easily spec'd from a number of antenna houses. So that issue is not being placed on this table. The rest of the gain budget is. Let the discussions begin. For example, what approach do the known "name" receivers (Kloss Model One, GE Super Radio) use? can a homebrewer do better? Which commercial house builds the best resonant chambers for the 108 Mhz frequency? Can be be done easily at home? how about the demodulation and audio portions? |
#3
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#4
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You need to look at your particular situation. It sounds like you are out
in the desert. Is this the case? Are there other strong FM stations nearby? Any others close in frequency? Sensitivity is relatively easy to come by. The "best" audiophile receivers are more about selectivity, which sounds like it might not be an issue in your case. There is a similar issue with antennas. Directionality is there more to combat multipath then it is to get gain. Is the terrain flat? If you are between a lot of buildings then nothing you do at the receiver will make up for what you don't do at the antenna. You are right about needing to get your antenna high, but for a single, point to point circuit, there is such a thing as high enough. More won't help. But less will hurt dramatically. The other big problem is getting the signal from the antenna to the radio. At FM frequencies, line losses are significant, as is noise pickup. If the signal is marginal, then you need to get an amplifier at the antenna. If what reaches the receiver is mostly noise then no amount of sensitivity at the receiver is going to help. At any given frequency there is only a certain amount of sensitivity that you can use. At FM broadcast frequencies, that amount of sensitivity is easily obtainable these days. You can probably do "better" in terms of sensitivity by building something, but you wouldn't hear the station any better ... in fact, probably worse by having too much of a good thing. ... "Alan Horowitz" wrote in message ... a city I visit frequently -or more precisely, it's exurban outskirts - has only one mellow-Jazz FM-broadcast station, the only one for many hundreds of miles. thus I have decided to build my own single-station hi-performance receiver to get the one station. I know enough to know that ideally, the bulk of the gain, directionality, selectivity should be at the antenna itself. Or even more to the point, tower height. At least ideally. And hi-performance single FM channel yagi's are easily spec'd from a number of antenna houses. So that issue is not being placed on this table. The rest of the gain budget is. Let the discussions begin. For example, what approach do the known "name" receivers (Kloss Model One, GE Super Radio) use? can a homebrewer do better? Which commercial house builds the best resonant chambers for the 108 Mhz frequency? Can be be done easily at home? how about the demodulation and audio portions? |
#5
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Thought I posted a reply yesterday, but it doesn't appear to have made
it. Before we head off into the weeds with all sorts of opinions, how about some clarification? I'd be interested in answers to several questions, and suspect others will add more. o What sort of distortion levels and signal to noise ratio are you wanting to achieve? o What level of desired signal will you be able to deliver to the receiver's input terminals? Will it be strong enough, and free enough from multipath, to make the desired distortion and SNR practical? o What levels and relative frequencies will strong potentially interfering signals be? -- Let's hope there's nothing significant on an adjacent channel, and nothing really big on alternate channels (+/-400kHz). o How skilled are you in RF and digital construction, and what tools do you have available for design, construction and turn-on/alignment? o Do you want the receiver to be portable and battery-powered, or can it be relatively large and line/mains powered? (o Why would you not just buy a good FM tuner, and perhaps just build a preselector if alternate-channel stations were a problem?) Cheers, Tom (Alan Horowitz) wrote in message ... a city I visit frequently -or more precisely, it's exurban outskirts - has only one mellow-Jazz FM-broadcast station, the only one for many hundreds of miles. thus I have decided to build my own single-station hi-performance receiver to get the one station. I know enough to know that ideally, the bulk of the gain, directionality, selectivity should be at the antenna itself. Or even more to the point, tower height. At least ideally. And hi-performance single FM channel yagi's are easily spec'd from a number of antenna houses. So that issue is not being placed on this table. The rest of the gain budget is. Let the discussions begin. For example, what approach do the known "name" receivers (Kloss Model One, GE Super Radio) use? can a homebrewer do better? Which commercial house builds the best resonant chambers for the 108 Mhz frequency? Can be be done easily at home? how about the demodulation and audio portions? |
#6
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#7
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For about the last 15 years I have been listening to NPR at 89.5 MHz while
riding my bike for an hour or two on nice days. There are several locations where many radios don't receive and lose the station and sometimes capture another close station. I've been buying used portables at garage sales for $10.00 or less and comparing their performance. So far I haven't found any of the Walkmans or Sports radios that are acceptable and to date the best has been a Sony ICF-34, much better than my Grundig Yacht Boy 400, but I can't risk it to try my Sony 2010. I've built and/or modified many radios and often thought about trying to make a better 89.5 radio but I don't think there's anyway I can beat the commercial jobs especially when I can get them for $10.00 or less. Generally I prefer not to use headphones and instead fasten the portable to my handlebars so I can hear the radio and local sounds. The radios take a pretty good beating but few have failed from the vibration or minor crashes. In the past I've lived in somewhat remote locations where I couldn't get the stations I wanted and the best solution was a good antenna with directivity and gain as high up as you can get it! But I can't do that on my bike. However if you come up with a good home brew solution please let me know. 73 Hank WD5JFR "Alan Horowitz" wrote in message ... a city I visit frequently -or more precisely, it's exurban outskirts - has only one mellow-Jazz FM-broadcast station, the only one for many hundreds of miles. thus I have decided to build my own single-station hi-performance receiver to get the one station. I know enough to know that ideally, the bulk of the gain, directionality, selectivity should be at the antenna itself. Or even more to the point, tower height. At least ideally. And hi-performance single FM channel yagi's are easily spec'd from a number of antenna houses. So that issue is not being placed on this table. The rest of the gain budget is. Let the discussions begin. For example, what approach do the known "name" receivers (Kloss Model One, GE Super Radio) use? can a homebrewer do better? Which commercial house builds the best resonant chambers for the 108 Mhz frequency? Can be be done easily at home? how about the demodulation and audio portions? |
#8
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"Alan Horowitz" wrote in message ... a city I visit frequently -or more precisely, it's exurban outskirts - has only one mellow-Jazz FM-broadcast station, the only one for many hundreds of miles. thus I have decided to build my own single-station hi-performance receiver to get the one station. I know enough to know that ideally, the bulk of the gain, directionality, selectivity should be at the antenna itself. Or even more to the point, tower height. At least ideally. And hi-performance single FM channel yagi's are easily spec'd from a number of antenna houses. So that issue is not being placed on this table. I lived in the Albany, NY area for many years, back when there were not too many local FM stations there (that is, the 1970's and early 1980's). I used an audiophile FM tuner board and a roof-mount Yagi FM antenna. Most of the local stations were southwest of my home. In any other direction but the southwest, I regularly pulled in stations up to 120 miles away. More distant stations were hit and miss, depending on tropospheric bending, etc. If your area is not saturated with local stations, you should have no trouble with a similar arrangement. |
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