we need to come up with a cheap to make tuneable am f/s meter to aid in tuning up hamiltons and sstrans. need to be tuneable and attenuable to allow for judging releative f/s so you can tell when the antenna is at peak resonance on the fundamental frequency as opposed to a harmonic something passive f/s meters and onboard t/p's don't accurately tell you.
most modern low end receivers do not offer large attenuation only a local dx setting.
The terms f/s and t/p tends to be greek to me...
But are you implying using a standard multimeter for tuning (as described in the Rangemaster manual) is not sufficiently an accurate method?
f/s = field strength
t/p = test points ? ( where you connect a multimeter on a circuit)
I use an old vintage 20 pound Sony receiver with a signal meter. It's a pain but it's the best I've got. I'd love to have something I could haul around in my pocket instead.
TP's are fine for a ballpark figure but an FS meter is the only way to know what's really being radiated from the antenna.
I consider it 'the last word'.
Andre
The last word is the perfect description for what we need to be exactly and perfectly compliant in the Part 15 camp.
Yes, we for sure need a field-strength meter that is affordable and has enough accuracy to tell us what we have going on with our RF output.
The Eff-Cee-Cee should be required to provide us with the tool they require us to have to monitor the signal we can't afford to monitor.
They should be the responsible party who sees to it that we have a usable field strength meter.
Only then will we have peace in the world and less turmoil.
"The Eff-Cee-Cee should be required to provide us with the tool they require us to have to monitor the signal we can't afford to monitor."
Who do you think pays for those fancy Potomac's they use that we can't afford to have ourselves?!!
I use a Workman SWR-3P. Accurate enough to tell me the antenna is peaked by simply placing the meter 1 half meter from the antenna, which is better than directly connecting to the antenna because that throws off the resonance peak as does nearby objects influencing the resonance.
For the accuracy at the flea levels sporting tuning and variable sensitivity it wont be a cheap meter. But designing one is not that big of a deal. Plenty of schematics on the web to hundreds if not thousands of fs meters.
Or we can all petition the goberment to buy us all a meter that we will end up paying for anyway..either way the common folk are footing the bill.
RFB
Woops, I mean, "neat meter." Thank you Dade City for that.
Since that meter is broadband, it will be unable to tell which transmitter it is registering. Here in the building, during heavy RF traffic, there are about six transmitters on the air with differing functions, therefore it would be necessary to field test them one at a time.
I also imagine that nearby 850kHz, 5kW, which comes in over the telephone, would probably be detected until sign off at sundown.
The meter would not report on exactly what frequencies it was showing on the scale.
Comments on all that?
the reason i say tunable is because with the electrically short antennas we use the 2nd harmonic can be as strong as the fundamental frequency in some cases. it would be hard to differentiate if you are tuning up the harmonic or main frequency. if you have something that register f/s only on the main frequency you'll be assured the antenna is properly peaked. the hamilton manual even explains this problem in their tuneup instructions. they offer a simple solution but i dont believe the sstran includes such a detail in their manual even though they use the same kind of atu as hamilton.
You mean, you guys don't all have Potomac FIM's to test your stations output??? Unbelievable!! Just kidding, mine is borrowed too... I was looking at something about a month ago, that I thought we could adapt into a cheap FS meter, let me see if I can dig up the link.
Tommy J.
Link found: http://www.northcountryradio.com/Kitpages/rffsm.htm
Maybe to simple but the Talking House ATU has a built in tuning meter that really makes tune-up easy.
The schematic for the ATU is HERE in figure 7 a few pages in.
Ignore the input transformer, tuning coils, etc., and just look at the metering circuit starting at the 10pf cap tied to the antenna whip and work towards the meter. Nothing special here, should be easy to find components.
Carl ...
These types of FS meters, where low power is concerned, need to be used a few feet from the radiator ... IOW, it won't be getting much interference from stations which are not on the same frequency for which you are testing, and you surely wouldn't be broadcasting on an occupied frequency, would you?
But, yep, a tunable FS meter would be the sure way. In my case, I used a rock-simple coil/germanium diode/cap/resistor circuit with a telescopic antenna, to which I att'd my multimeter, which is very sensitive and reads mv out to 3 places. Still took me hours up-and-down the ladder to get it to peak, but it's been golden since then.
It's 11:00pm here, and I'm still getting a very useful signal most places in my small town.
"But, yep, a tunable FS meter would be the sure way."
So...which comes first...the tuning of the chicken or the tuning of the egg?
IE...when tunable FS meter is not peaked itself, what is the reference then to peak the FS meter first prior to tuning the antenna peak. How is calibration to be maintained?
I suggest a digital tuned FS meter, no fuss no muss and no wasted time up and down ladders all day.
Now that I think about it..why not just do what I did and add a FS circuit to the antenna system itself and send that reading to a meter indoors and control the tuning of the antenna with a servo..again from the comfort of indoors.
Hobby Engineering dot com has all the necessary ingredients for the remote mechanical tuning system. The rest is up to your imagination and stock of junk parts.
RFB
Several people have mentioned the Tecsun PL390 and Grundig G-8 for their metering.
Tommy J
The conversation for me has reached a "V" in the road and gone off on two different paths.
On the original road the subject (I think) was a "f/s" meter, namely a field strength meter capable of reading the field strength out in the open air and get an idea of the energy at a certain distance.... which is why the Potomac was brought into the conversation.
But the "V" took us also on path 2 where we we talked about meters to simply peak the output of a transmitter without getting a field reading.
THEN I did an interesting and (self)-informative brain trick..... I imagined a radio receiver that would simultaneously reproduce every frequency from 100kHz up to 500mHz, which is the bandwidth of the f/s meter from Universal Radio. That would be one noisy batch of radio signals!! That meter would ONLY be of use up close to an antenna for peaking. A more precise field reading would absolutely require a meter tuned to the specific frequency to be measured.
There ought to be a modification to a low-end portable AM radio to create a "t/p", test-point, to attach a meter. Then we would have tunable and meter. The final step (not simple, but maybe possible), would be to calibrate the accuracy of the meter scale.