I mentioned this a couple of years ago, I
think. This story comes from 1969.
BVR comes comes from WBVR, Buena Vista Radio,
Part 15, transmit frequency not yet determined.
I mentioned this a couple of years ago, I
think. This story comes from 1969.
BVR comes comes from WBVR, Buena Vista Radio,
Part 15, transmit frequency not yet determined.
I thought about it again because the Part 15
transmitter in use was a Lafayette KT-195.
We have been talking about that old transmitter
lately, so I thought I would tell this story again.
The KT-195 was a tube design AM Part 15 transmitter.
It has generated a lot of discussion on this board,
especially lately, so that's all I'll mention here.
In this particular "broadcasting" experiment, the KT-195
was being fed by a record player. The set-up was in
my parent's rec-room, which was part of the cellar.
(Wreck room, maybe?) The set-up was sitting on
the counter. The transmitting antenna was a 10 foot
piece of 300 ohm twin-lead. I don't remember if both
sides of the twin lead were connected or not. Here's
the important part - the twin lead was sitting on the
rec room floor. So we are talking about an underground
antenna. No attempt was made to hang up the antenna
on anything. It was just on the floor.
The transmitter seemed to radiate on many frequencies
at the same time. That's why I mentioned that the
transmit frequency was undetermined. The transmitter
may have been unstable resulting in spurs, or the radio
in the house may have been overloaded, or both. We could
not figure out what frequency from the transmitter was
getting out, if any.
End of story, almost.
i kept this thing running a lot for fun. So one day I was sitting
there listening to a song from the KT-195, going through the
radio. I didn't have a lot of records, so it was pretty boring.
I still didn't know what frequency was "right," so I just picked
one and was enjoying it.
The phone rang. It was my best friend 3000 feet away on the
other side of the "Buena Vista Golf Course" (Which explains
how WBVR got it's name.)
He was hearing WBVR at his house! 3000 feet away, on a
Knight Kit R100A receiver with a 90 foot antenna wire outside.
The signal strength meter said S7. The frequency he was
listening to was 2100 kHz. That's where WBVR was really
getting out.
So, here we are, more than 40 years later. I still don't know
how this KT-195 could have gotten so far with just a 10 foot
antenna on the cellar floor!
I have to run, so I can't proof read this - I hope it's OK. So what
do you guys think of this story. Does anybody have an explanation
for how the signal got out so far?
Best Wishes,
Bruce, DOGGRADIO STUDIO 2
210kHz is not much higher than the top of the AM dial, but it would still be closer to matching a 3-meter antenna than any lower frequency. But the other major thing was your friend's outdoor antenna. That may be the biggest factor.
One-half of 2100 would be 1050, which could have been your fundamental operating frequency.
Oh, and golf courses are kept well watered, so the BVR Effect was no doubt helped by that.
You already answered the question in your description of that transmitter's "saw tooth" mood..sending out a bunch of harmonics along with the main carrier..and is why your friend
3000 feet away picked up that harmonic on 2100Khz.
The combination of your "floor" antenna, the golf course ground, the receiver type and 90 foot wire antenna, and your transmitters very dirty spectral output, all combined to let your friend receive the signal.
This is why proper antenna tuning and matching and low pass filters are so important..even for Part 15 flea power.
It might be 100mW on MW, but if its dirty, it could be a lot more on another band.
RFB
I think you guys are correct on all counts.
And I never thought about the golf course
being part of this thing - but it sure makes
sense.
In 1969 I did a frequency search in order to
find a good legal AM frequency. 1610 and
above was illegal in those days, as we all know.
I chose 1460 in 1969. Today, more than 40 years
later, the status of 1460 is about the same.
One thing did change on the AM band after all of
those years. There was a 1590 in Connecticut
in 1969. That station has since gone dark. So
1590 is now pretty quiet during the day here.
If that 1590 didn't exist in 1969, I would have
tried to put WBVR there.
But as we all know, that never happened. 2100 kHz
is a pretty weird place, and I did not like the
fact that it did not comply with the rules. So,
even though I was astonished by the "BVR Effect,"
I did not use the transmitter. I was starting to
learn about ham radio then, and was gearing up
to run 75 watts on 80 meters. I did not want
to do anything illegal - and I was very serious
about that.
Since that KT-195 wanted to transmit in the
"Marine Band," we eventually chucked it. (Lacking
the tech knowledge to try to set it right - also,
we were tired of all the electric shocks we got from
the thing.)
The KT-195 I have now belonged to the guy on
the other side of the golf course. It doesn't
work. But I don't care. Actually, this KT-195
sort of belongs to both of us now, I guess. It
really doesn't matter what house it is in. We are just
preserving it - like the Gates board, the LPB RC-6A
CC transmitter, the Akai GX-4000D reel to reel
deck, and all the other stuff.
That guy on the other side of the golf course
and I have been good friends since 1968.
In those days, we lived 3000 feet apart.
Now in 2012, we both still live in the same town, but
of course in different houses, and we are about a mile
apart, I think. And we are about 2 miles east of where
we were. When DOGGRADIO was running on AM 1690, he
could hear it in his driveway on the car radio without
amy problem. That was about 3 years ago.
My friend is a ham and a broadcast engineer. Whenever I
get the 13.560 transmitter going - well that project is
really for him - so he can hear my station easily in his
house in his ham shack.
Some day.
Best Wishes,
Bruce, DOGGRADIO STUDIO 2