Indoor FM boost with no cables?
 

On 7/26/2014 12:32 AM, Jeff Liebermann wrote:
On Fri, 25 Jul 2014 14:21:07 -0500, Lostgallifreyan
wrote:

I hope to boost the incoming signal to override the ocal RF mush from nearby
flats, and to do this for a portable receiver so I want no cables attached to
it at all. I have considered two possible ideas:

Hey Jeff,
Is it possible to build a tuned loop connected to the backside of the
radio, to cover the FM band. I never tried a loop at 100Mhz.
Mikek



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Indoor FM boost with no cables?
 

On Sat, 26 Jul 2014 09:22:08 -0500, amdx wrote:
Hey Jeff,
Is it possible to build a tuned loop connected to the backside of the
radio, to cover the FM band. I never tried a loop at 100Mhz.
Mikek

Sure. Google for VHF magnetic loop antenna.
https://www.google.com/search?q=vhf+magnetic+loop+antenna&tbm=isch
They work so-so, but have the same problem as the HF version. The Q
is very high resulting in extremely narrow usable bandwidth. In order
to make it work, there would need to be some way of tuning the loop to
frequency. Making it track the receiver frequency would be a big
plus.

http://www.m0ukd.com/wordpress/homebrew/magnetic-loop-antennas/
He forgot to insert a series tuning cap in the gamma match, but
otherwise, it should give you an idea of what's involved.

http://www.iw5edi.com/technical-articles/144-mhz-magnetic-loop-antenna
Much better.

Anyway, recalculate for 100 MHz and it should work.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Indoor FM boost with no cables?
 

On 7/26/2014 10:15 AM, Jeff Liebermann wrote:
On Sat, 26 Jul 2014 09:22:08 -0500, amdx wrote:
Hey Jeff,
Is it possible to build a tuned loop connected to the backside of the
radio, to cover the FM band. I never tried a loop at 100Mhz.
Mikek

Sure. Google for VHF magnetic loop antenna.
https://www.google.com/search?q=vhf+magnetic+loop+antenna&tbm=isch
They work so-so, but have the same problem as the HF version. The Q
is very high resulting in extremely narrow usable bandwidth. In order
to make it work, there would need to be some way of tuning the loop to
frequency. Making it track the receiver frequency would be a big
plus.

I expected to have a tuning cap on the loop to tune to his frequency
of interest. I don't know about polarization, but he may be able to
rotate out some interference with a loop.


Mikek


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Indoor FM boost with no cables?
 

Jerry Stuckle wrote in news:lr0d4e$spo$1@dont-
email.me:

That does not mean it's not operating illegally. Even with such a tag,
it can be emitting a signal illegally.

ALL potential sources of RF have limits on their emissions. Exceed
those limits and they are not operating legally. It may be due to
shoddy workmanship or a problem with the device itself.


Could be so, but like weed-smoking, popular round here, though I haven't done
it myself for at least twenty years and do not like it, is a live-and-let-
live thing, not a call-the-police thing. Also, if I start shouting about a
small bit of interference, people might start shouting about not liking my
solar panels outside the house looking (to their eyes) unacceptably ugly,
etc...

Also, the cost of the expert witness to prove it in court is a cost so
extreme in proportion to the problem that I won't consider it viable.

I suspect it's well within limits actually, no worse than half the small
collection of stuff I have like mice and keyboards emit. It's just what was
left after I'd turned off all I could control, in a basement that very little
external RF penetrates into anyway. Hence me steering the discussion back to
the notion of a gentle boost for the immediate locality. :)

Indoor FM boost with no cables?
 

amdx wrote in :

I expected to have a tuning cap on the loop to tune to his frequency
of interest. I don't know about polarization, but he may be able to
rotate out some interference with a loop.


Slightly cubersome for my situaion but technically true, so a nice idea.
Thanks.

Indoor FM boost with no cables?
 

On 7/26/2014 1:19 PM, Lostgallifreyan wrote:
amdx wrote in :

I expected to have a tuning cap on the loop to tune to his frequency
of interest. I don't know about polarization, but he may be able to
rotate out some interference with a loop.


Slightly cumbersome for my situation but technically true, so a nice idea.
Thanks.

Ya, I'm thinking a 3 or 4 turn loop to fit the back of the radio.
I had to work all day, earlier I had thoughts about putting one my GE
Suoerradio III just to see if it works. A spiral form may be less
cumbersome. I have a bunch of ten pf caps, but I haven't calculated
anything yet so don't know if 2pf to 10pf would resonate with a
reasonable size coil.
Mikek

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Indoor FM boost with no cables?
 

On 7/26/2014 10:57 AM, amdx wrote:
On 7/26/2014 10:15 AM, Jeff Liebermann wrote:
On Sat, 26 Jul 2014 09:22:08 -0500, amdx wrote:
Hey Jeff,
Is it possible to build a tuned loop connected to the backside of the
radio, to cover the FM band. I never tried a loop at 100Mhz.
Mikek

Sure. Google for VHF magnetic loop antenna.
https://www.google.com/search?q=vhf+magnetic+loop+antenna&tbm=isch
They work so-so, but have the same problem as the HF version. The Q
is very high resulting in extremely narrow usable bandwidth. In order
to make it work, there would need to be some way of tuning the loop to
frequency. Making it track the receiver frequency would be a big
plus.

I expected to have a tuning cap on the loop to tune to his frequency
of interest. I don't know about polarization, but he may be able to
rotate out some interference with a loop.


Mikek


I've* calculated a 6 inch loop made with a #12 or #14 wire will
resonate the FM band with a cap between 6.5pf and 10pf. Roughly!
Now, I'll see if I can generate the gumption in the next couple
of days to build it to see if it has any positive effect.
I hope someone beats me to it.
With an AM loop and radio the signal couples to the internal loop very
well, I don't know how well you can couple a signal into an FM radio.
Mikek

* actually I used a couple of online calculators.

http://www.deephaven.co.uk/lc.html

http://www.daycounter.com/Calculator...lculator.phtml

Indoor FM boost with no cables?
 

On Sat, 26 Jul 2014 09:02:44 -0500, Lostgallifreyan
wrote:

Nope. It's one of those consumer widgets, one o millions, that have a
disclaimer saying that some limited interference must be accepted. Knowing
this, it isn't even worth trying to police the issue, and probably impossible
anyway. Computer based stuff just does this to us, there's no stuffing THAT
genie back in the bottle now.

Much depends on the device causing the problem. It's often cheaper
and easier to just buy the owner a new device instead of trying to fix
it. I've done that a few times with Chinese junk that never had a
prayer of meeting FCC Part 15 incidental radiation limits. So far,
I've replaced one ethernet switch, one 4 line phone, and 2 security
cameras in the neighborhood. Also, a mess of junk switcher type cell
phone chargers.

However, you can't do that if you don't know what's causing the noise.
So, take your portable radio, wrap it in aluminum foil to REDUCE the
sensitivity, and snoop around the building until you find the culprit.
The rest you can figure out yourself. Hint: Diplomacy works.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Indoor FM boost with no cables?
 

Jeff Liebermann wrote in
:

Much depends on the device causing the problem. It's often cheaper
and easier to just buy the owner a new device instead of trying to fix
it. I've done that a few times with Chinese junk that never had a
prayer of meeting FCC Part 15 incidental radiation limits.

That could work. :) I agree, the price of the widget and a bit of diplomacy
might go further than any other effort. If it becomes a problem I'll try
that.

Indoor FM boost with no cables?
 

amdx wrote in :

I've* calculated a 6 inch loop made with a #12 or #14 wire will
resonate the FM band with a cap between 6.5pf and 10pf. Roughly!
Now, I'll see if I can generate the gumption in the next couple
of days to build it to see if it has any positive effect.
I hope someone beats me to it.
With an AM loop and radio the signal couples to the internal loop very
well, I don't know how well you can couple a signal into an FM radio.
Mikek

* actually I used a couple of online calculators.

http://www.deephaven.co.uk/lc.html

http://www.daycounter.com/Calculator...lculator.phtml


This is nice because it beats the issue with two ways to be selective. Even
so, I have to have one last shot at the broadband notion: could a 6dB boost
with one of those MAR6-based antenna amps be worth a shot? Driving a local
diple, taped to a doorframe perhaps, in the centre of the flat? Given the
tiny size of those IC's I doubt the amount of power getting out of the flat
will be a nuisance, especially given its reluctance to allow RF in (except
through the celing, and a dipole taped vertically to a doorframe isn't going
to send a lot upwards either.. To some extent the business may be eased by
the fact that the two frequencies I'm most keen to get, 91.5MHz and 93.7MHz,
aren't far apart. If there is ANY chance this can be solved with no
modification or encumbrance to the tiny radio I intend to carry from room to
room, that's the way I want to do it.