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I conducted an experiment today using a prototype copper wire 2m dipole at a ground level base station (noted on images) and a FT2D HT with an SRH77CA antenna. I recorded my transmissions using a laptop at the base station, and recorded my GPS coordinates as I moved.

The base station received all of my transmissions up to ~2km at a signal strength of ~S9. However, after 0.5km the signal became unreadable (signal report would be 1/5).

What might be the cause of this lack of readability, but strong reception? Could it be the dense steel/glass/concrete disrupting propagation path? I would have guessed that this would cause the signal strength to be diminished in proportion to the readability.

What kind of things could I do to improve readability of my signal (Maybe it's really just getting an antenna on the roof instead of on ground floor)? - Thanks! KC9PPX/HB3XRS

Weather condition: clear skies

3D view of GPSOverhead View

Update 10-SEP-2019

I repeated the experiment again today, but this time I connected the FT2D to my homebrew dipole to act as my base station instead of my FT857.

This time I carried an FT-4X HT with a factory rubber duck. Again inside my pack next to a bag of water. The signal was still unreadable for all transmissions beyond the first checkpoint (same as before). But I can hear one or two words in some of the static, which is an improvement over the last time I ran the experiment. Could have something to do with putting my homebrew dipole on the FT2D!

Weather condition: clear skies.

I think the next time I run this experiment I will put my antenna, radio and computer on the roof of my building. I hadn't thought of using the FT2D as a base station before, it's much more portable and easier to hide than the 857. My guess is this will make a massive difference in readability, but let's see.

I'm using Audacity to evaluate signal strength. I would still guess S9 for each transmission. enter image description here

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    $\begingroup$ Welcome to Amateur Radio Stack Exchange! I think more information is needed, if you could please edit your question to include... Were there hills involved? Buildings? Tunnels? How did you move (walk? Car? Scooter?), and with what sort of direction (straight line? Spiral? Random movement?). Is the 2m base antenna vertical or horizontal? How high? I do not understand the 2km vs 0.5km; from where? Thanks! $\endgroup$
    – Chris K8NVH
    Commented Sep 7, 2019 at 16:38
  • $\begingroup$ Thanks! I added some images to improve the context. HT was in a backpack (with one of those water bags in it...) the whole time. Elevation gain in the forest is ~100m maximum. $\endgroup$
    – Justin
    Commented Sep 8, 2019 at 12:31
  • $\begingroup$ Elevation gain isn't the issue -- are there hills between the antennas. Also, if the water is between the antennas, it may also attenuate the signal a bit. And the j-pole is a complete dipole, where the whip on the radio is just a monopole and (without a counterpoise) will not work well if they radio isn't being held. $\endgroup$
    – user10489
    Commented Sep 8, 2019 at 14:06
  • $\begingroup$ Good update, thank you. How did you measure signal strength and how did you measure readability? $\endgroup$
    – Chris K8NVH
    Commented Sep 9, 2019 at 1:08
  • $\begingroup$ Can you look at one of the "poor readability" samples in an audio analysis tool such as Audacity? I think that will give useful clues. $\endgroup$
    – Chris K8NVH
    Commented Sep 9, 2019 at 1:27

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Not an expert here, but since I don't see any answers yet these might be possible reasons:

  • during the first leg of the trip, it seems like you had more or less line of sight. After that, there seem to be more buildings in between you and the base station. Maybe you had lots of reflections/multipath towards the receiver (the receiver receiving the signal not just directly from the source/ht, but also from reflections from buildings/... These have a phase shift depending on the reflection and additional transmission path length. Mix all that together and you might end up with a strong but possibly useless signal.)
  • was the signal reception back as it should during the last part of the trip? So, did you have a similar transmission quality when you moved away from the base station as when you got back closer to it? If not, a drained battery in the handheld might be a possible cause...

-edit: after looking up your ht, I doubt the battery could be the cause. I noticed this behaviour with a simple old Kenwood th22e. I think the empty battery voltage dropped on each transmit, triggering a brown out reset, starting transmit again and so on. On your ht you would see the screen going blank and you would notice the restart so not a likely cause...

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  • $\begingroup$ "steel, concrete, and glass" says multipath in at least three languages. The phase shifts will convert a clean FM signal into a dozen mixed signals, and your receiver can't "capture" because they're identical in strength, so you get all of them, with a huge garble factor. $\endgroup$
    – Zeiss Ikon
    Commented Sep 9, 2019 at 18:25
  • $\begingroup$ Is there a way to model reflections/multipath? I wonder if there is a way to "see" what this might look like. $\endgroup$
    – Justin
    Commented Sep 10, 2019 at 17:20
  • $\begingroup$ I don't know what you used to measure and log your signal strength or how much background you have with sdr, but I suppose you could use GNU radio to emulate this. Take a couple of copies of the same fm signal, mix them together with semi random phase shifts (delays) and amplitudes. That should resemble the effect of multipath. $\endgroup$
    – Dieter Vansteenwegen
    Commented Sep 10, 2019 at 20:03
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Because you had a strong signal, I am thinking this is either a measurement error (clipping, for example) or a transmission error (high volume background noise, for example) of some sort. I will keep asking "dumb questions" in comments and update this answer as appropriate.

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