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Author Topic: Transmitting woes - Not being heard - Out Of ideas  (Read 6773 times)
AA4PB
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« Reply #30 on: February 06, 2013, 05:47:52 AM »

The SWR doesn't tell you a thing about how much of the applied signal is radiated. A 1:1 SWR only tells you that transmitter power is being coupled into the antenna. The antenna could be dissipating all of the applied power as heat in loss rather than radiating it (i.e. a dummy load). The antenna could also be enclosed in reflective or absorbing material that prevents the signal from getting outside the enclosure.
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KB8LOG
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« Reply #31 on: February 06, 2013, 06:28:15 AM »

Thanks AA4PB and W5DXP. Looks like the next step is the field strength meter. Up until recently I was not at all familiar with them, though I was aware of their function. After doing a bit of reading I have a couple questions.

- Should I concern myself with simply detecting whether or not the antenna is radiating anything at all?

- I've built a few kits, but beyond that I'm not an electronics person, though I do hope to begin learning more once I can get this current roadblock solved. After looking at some of the schematics on that link (thanks for that DXP!) I am assuming that any analog meter will work. Is that right? I think I've got a one or two at home that I salvaged from some old garage sale purchases.

One other thing that I'm curious about is how a field strength meter will behave around a magnetic loop. Just a couple days ago I was reading something, I believe it was a forum post somewhere, where someone stated that they had used a FSM to check their magloop. They were surprised to find that it didn't detect anything until they were quite some distance from the antenna - I think it may have been a full wavelength away. I suppose I could simply throw a wire up to make sure that the transmitter is transmitting and an antenna is actually getting out at all, and then worry about the loop.
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AC2EU
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« Reply #32 on: February 06, 2013, 06:47:12 AM »

from LOG:
Quote
The readings I am getting at the currently tuned resonant frequency of 7.064 MHz are resistance of 50 ohms, reactance of 0 ohms, and SWR of 1:1.

That sounds almost too perfect! As you sweep the frequency below and and above, does the reactance change?
As an experiment, check the  reading on the analyzer with the antenna disconnected from the tuning system to see if it changes or not. I think you are tuning the coax or most of the energy is bouncing around in  the "tune box" which may make it look like a 1:1 but the power is not getting into the antenna. Like I said before, it is possible to tune into a piece of coax...

BTW how long is that antenna at that you are using at 7 MHZ?
 
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N4CR
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« Reply #33 on: February 06, 2013, 06:58:26 AM »

I'd advise the same with the exception that I'd target 20 meters.

Then he wouldn't be able to use SSB.

Oh, that license thing. I see. Well then, the first thing I'd recommend is a license class upgrade to General class. It's not that much harder than a Tech class license test.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
KB8LOG
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« Reply #34 on: February 06, 2013, 07:56:21 AM »

from LOG:
Quote
The readings I am getting at the currently tuned resonant frequency of 7.064 MHz are resistance of 50 ohms, reactance of 0 ohms, and SWR of 1:1.

That sounds almost too perfect! As you sweep the frequency below and and above, does the reactance change?
As an experiment, check the  reading on the analyzer with the antenna disconnected from the tuning system to see if it changes or not. I think you are tuning the coax or most of the energy is bouncing around in  the "tune box" which may make it look like a 1:1 but the power is not getting into the antenna. Like I said before, it is possible to tune into a piece of coax...

BTW how long is that antenna at that you are using at 7 MHZ?
 

I worried someone might think those numbers were suspect. Smiley I was actually surprised and thrilled when I was able to get the analyser to show those readings. I should note that once I finally found the frequency that the magloop was tuned to, the readings were fluctuating while I was just watching the LCD on the analyser, but the fluctuations were very slight (0.1 SWR and 1 ohm resistance).

I think I see what you're getting at with the experiment of reading the analyser while the antenna is disconnected. The readings do change without an antenna or just a piece of wire. With the magloop connected it did require some patience in order to match the analyser to the frequency that the magloop capacitor was tuned for. Even slight adjustments to the frequency on the analyser impact the reactance and resistance.

The magloop is 16' of 0.75" copper pipe soldered in the shape of a square. I do have a mechanical joint (union fitting) in the center on the bottom, right below the coupling loop so that I can decouple both halves of the loop and store them more conveniently. The coupling loop is some rather rigid scrap wire (I'd have to check the gauge) roughly 4.5' in length and formed into a square, though I think the top and bottom may be a tad bit longer than the other sides. The capacitor is not ideal. It's got a range of around 50pF to 365pF I believe. This coming weekend, assuming the package gets here on time, I'll be replacing it with one that has much better plate spacing and a range of 23pF to 160pF. So tuning the cap should be much easier. I may wind up replacing the coupling loop with a gamma match so that it'll work on more bands, but for now I'm just going to stick with what I've got.
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KB8LOG
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« Reply #35 on: February 06, 2013, 07:57:48 AM »

I'd advise the same with the exception that I'd target 20 meters.

Then he wouldn't be able to use SSB.

Oh, that license thing. I see. Well then, the first thing I'd recommend is a license class upgrade to General class. It's not that much harder than a Tech class license test.

Yep! That's among my current goals. I likely would have passed the general exam a couple years ago had I not grown so frustrated by the same problem I'm attempting to solve now, and then getting laid off from my job at the time.
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W5DXP
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« Reply #36 on: February 06, 2013, 11:09:44 AM »

One other thing that I'm curious about is how a field strength meter will behave around a magnetic loop.

The pickup antenna does make a difference. Some are more sensitive to the electric field and some are more sensitive to the magnetic field. Ferrite rod antennas, as used in a lot of AM radios, are more sensitive to the magnetic fields.
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KB8LOG
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« Reply #37 on: February 06, 2013, 07:13:31 PM »

I just fired up my Drake receiver without an antenna. I was able to hear the CW from my Icom on the Drake. The frequency on the Drake was essentially a match.
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W5DXP
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« Reply #38 on: February 07, 2013, 04:59:37 AM »

I was able to hear the CW from my Icom on the Drake.

Use the Drake as a signal strength meter. Take it outside and see if you can hear the Icom.
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K5LXP
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« Reply #39 on: February 07, 2013, 06:04:25 AM »

Data point - several of the $5 hamfest special CB SWR meters I own have a field strength meter built in.  They come with a short 6 or 8" whip and are self powered.  Being "relative" you don't know what that actual field strength is in V/M but kept in a fixed location in relation to your antenna under test you can make some useful comparisons.


Mark K5LXP
Albuquerque, NM
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K1DA
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« Reply #40 on: February 07, 2013, 10:27:52 AM »

WHen you are starting from scratch, one of those  CB swr bridges with a field strength function is not a bad idea. 
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VE3FMC
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« Reply #41 on: February 09, 2013, 08:15:32 AM »

I was able to hear the CW from my Icom on the Drake.

Use the Drake as a signal strength meter. Take it outside and see if you can hear the Icom.

Good idea but how is he going to transmit and be outside at the same time?  Wink

LOG, why not build a dipole for 10 or 15, string it up along the ceiling/wall and see what happens. Since you are messing with loops, etc that may be half your problem.

A dipole cut to frequency would work better IMO , even if it is indoors. Better yet, string a wire out to those trees at night. Tune it and see if you can make contacts on 40 at night using CW.
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KB8LOG
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« Reply #42 on: February 09, 2013, 09:47:49 AM »

I had contemplated the issue of being at the transmitter indoors and receiver outside at the same time. Save for a system of pulleys or some contraption, I haven't found a solution. Smiley Plus the Drake is rather heavy and I'm not sure where I'd set it up.

Still working on the field strength meter. Between the weather, being busy, and not having all the parts handy, I have not yet had a chance to work on it. I do have a question though - once I have a functional meter, what exactly am I going to be doing? I understand that it'll detect an outgoing signal, but is there a strategy involved with using such a meter in a situation like my own?

This may be a non-issue, but I have been meaning to ask about it here as I am curious whether or not it could have any bearing on my issues. There is a power substation about 150 or so yards from my apartment. Is there any chance it could be hampering my signal when I transmit?

VE3FMC - I think I'll try that. I have a 40 meter dipole, but it's nothing special, so I don't mind modifying it. Besides, in it's current state it has not gotten me anywhere, and I can't even put it up inside the apartment unless it is U-shaped.
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W5DXP
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« Reply #43 on: February 09, 2013, 10:56:07 AM »

I had contemplated the issue of being at the transmitter indoors and receiver outside at the same time.

You could always run a long pair of wires for remote CW keying purposes. I would use a relay.

I get my wife to help me perform a remote test using our cellphones to communicate. My IC-756PRO has a button that, when pushed, sends:

"test de w5dxp" in morse code. Since I am in control and IDing, I don't see a problem. I say, "push the button now" and she does.

I did have a remote control setup in AZ. I could be driving home from work talking on my uhf HT which was demodulated at my house and remodulated on an HF frequency. Same in reverse for receive. I could even run slow CW using the PTT button on my HT.
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KASSY
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« Reply #44 on: February 09, 2013, 11:01:01 AM »

Hopefully you are only trying to call strong stations.  Any kind of indoor antenna is a compromise.   Do you have the IC-718 set for full power?  Do you know how?  Please explain that technique.

I have seen many newcomers have difficulty making QSOs because of operating technique.  One fellow who claimed his station was not working would tune in someone sending CQ, and listen.  "CQ CQ CQ CQ DE CALLSIGN CALLSIGN CALLSIGN CALLSIGN K".  Then the fellow would send "CQ and his callsign".  That's not a way to answer a CQ.  The CQing station would either think someone was trying to steal his frequency, or that he accidentally took over someone else's frequency.  It's not going to get a reply!  When answering a CQ, you must send the CQing station's callsign...once, twice, thrice, dependent on how strong you think your signal is going to be...then DE, then your callsign a few times then K or KN.

Also, how good is your CW?  I've heard CW on the air that was utterly uninterpretable.

If you could make an audio recording of your attempt to make a QSO, it would be easier for us to evaluate every possible aspect.

GL

- k
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