Uncategorized

The ever-vigilant mrklingon writes
Astrodome Radio Station Blocked –
Wired News – Sep 8, 2005

HOUSTON — KAMP 95.3 “Evacuation Radio
Services”, a low-power FM station for Hurricane Katrina evacuees housed at the Astrodome, is still stuck in limbo…

The ever-vigilant mrklingon writes
Astrodome Radio Station Blocked –
Wired News – Sep 8, 2005

HOUSTON — KAMP 95.3 “Evacuation Radio
Services”, a low-power FM station for Hurricane Katrina evacuees housed at the Astrodome, is still stuck in limbo…

Although the group trying to
organize the station has wrangled three 90-day licenses from the FCC,
as of Thursday, they were being stymied by a handful of temporary
administrators content to maintain radio silence.

Full Text

www.wired.com

WIRED is quite a friend to low power broadcasting – check them often for great stories!

WCRV, aka “The Antenna Guy” writes: After what amounted to a TON of research, I have selected both an FM
transmitter and a FM amp…

WCRV, aka “The Antenna Guy” writes: After what amounted to a TON of research, I have selected both an FM
transmitter and a FM amp…

It’s been an on-going project of mine ever since I got the sstran AM on
the air.

I am going with an EDM-100mW unit which will feed a FMB-2 ~2.5 watt
amp.

The only question now (which may seem silly since I’m the “antenna
guy”)
is which antenna I will use. I know it needs to be 50 ohm, and it also
needs to be VERY small, and here in lies the problem.

However I have two clear FM frequencies here, and with the simple wire
antenna, I should be able to cover much more than just the immediate
area, especially with the amp.

I’ll be experimenting with the transmitter probably this time next
week,
alone with the wire antenna. I’ll add something a little more exotic
(like the old-time TV dipole) and if I find something affordable and
SMALL, I’ll look to an antenna to complete the project.

This may mean more big things for NJRM: I do know how to build some
very basic (but large) FM antennas. The installation at NJRM will be
simple. But for here I need something inconspicuous, which means
“testing, testing, testing”.
To be certain, if I get a mile out of the EDM (even without the amp) I
will be very happy right here, since all the homes are concentrated in
one area; farmland all around us.

Will keep you posted.
Carl

Thank you for emailing WCRV/”THE ANTENNA GUY”
I welcome your questions about our antenna!
Most information can be found on our website
http://antenna18431.tripod.com/antenna.htm

Special orders welcome; Churches and Schools welcome to apply for
discounts.

New products for part 15’ers added as soon as they are available! We
now accept PayPal!
Our part 15 am radio station website:
http://wcrv1540am.tripod.com/wcrv.html

Editors note: Well, er, uh, um, that doesn’t sound quite part 15, Carl, but we’ll be interested to hear about how it turns out – C&D, or NAL 🙂

Curious about Radiation Efficiencies for Part 15 AM Radiators? If you haven’t visited our forums lately, you’ve missed some phenomenal discussions…

Curious about Radiation Efficiencies for Part 15 AM Radiators? If you haven’t visited our forums lately, you’ve missed some phenomenal discussions…

One of our newest forum members, a broadcast engineer who posts as Rich, dropped in with some antenna simulations.

Be sure to check the antenna tuner thread, and see your humble editor learn a valuable lesson in the value of simulations!

Best of all, Rich took a moment to summarize his findings in an nice PDF file, which you can download here:

Radiation Efficiencies for Part 15 AM Radiator

Enjoy!

This looks like a developing story, great photos, too…

This looks like a developing story, great photos, too…

East Lawton Community Radio reports, via their web site, that:

“The AM transmitter antenna equipment has arrived! The construction detail and workmanship is outstanding! Excellent work Carl! (the antenna guy).”

Here’s a teaser photo, linked from the ELCR web page:

Be sure to visit the East Lawton Community Radio web page at http://www.geocities.com/ab5ui/ELCR.html

ELCR says to be sure to chek back often, as more info will be posted soon – Drool 🙂

I have seen quite a few programs mentioned on Part15.US for broadcast radio automation software…

I have seen quite a few programs mentioned on Part15.US for broadcast radio automation software…

but all that I can remember have been for DOS or some version of Windows. I have finally found a program for those hardy souls who run Linux.

Rivendell is FREE automation software developed for broadcasters by broadcasters. According to the Web site, “Rivendell aims to be a complete radio broadcast automation solution, with the facilities for the acquisition, management, scheduling and playout of audio content.”

More details are available on the Rivendell page of the Salem Radio Labs Web site:

http://www.salemradiolabs.com/rivendell/

Version 0.9.48 of Rivendell was released on Monday, August 8th, 2005. The release announcement is at:

http://lwn.net/Articles/146667/

(Don’t be put off by the version number. Most Linux software starts off as a 0.1 or even 0.01 version, and is quite polished long before the magic 1.0 release.)

From time to time, a visitor will ask how to choose the right transmitter for a successful Part 15 AM BCB operation…

From time to time, a visitor will ask how to choose the right transmitter for a successful Part 15 AM BCB operation…

Since each operator will have different needs, interests, skills, budgets and content goals, I really don’t know if there is an ultimate answer. What follows is a general approach, and shared here for comments and suggestions.

I’d say there’s four areas to look at, power use, modulation, audio processing and RF buffering.

Power Use

Many folks use the power input limit criteria for compliance – that’s the 100mW standard that’s frequently kicked around.

That means you get 100 mW of power DC input into your XMTR, and it’s up to your XMTR to get the very most RF out of the 100mW DC in.

Good oscillator and buffer designs help this outcome a great deal, so you’ll want to find XMTR designs that get the most RF out of the power that’s dribbled in.

PLL or XTAL seems to work best for AM BCB, VCOs have never really made me too happy when you’re shooting for 24/7-365

So job #1 is getting the most carrier out of 100mW DC input. Some XMTRs are more effective at squeezing out every drop.

Modulation

Grabbing your audio input and effectively modulating your carrier is the next job your XMTR needs to do well. Some XMTR designs will be better at this than others, and the effectiveness of the modulation of the carrier will have a big impact on how happy you are with your station.

A short example – I had a PanAxis AM100, and I was very unhappy because it seemed to have a very short range. I contacted PanAxis and they gave me some modulation adjustment tips. I made the adjustments, and all of a sudden I could hear my XMTR a mile out. It seems the radio waves were actually going quite a distance, but the carrier wasn’t modulated well enough for my radio receiver to reproduce any audio – I was getting out, I just couldn’t hear me!

Adjustments aside, some XMTRs modulate better than others, and some modulation stages can swallow higher audio outputs – that makes your range seem greater because you can “kick over” the detector in receivers that are farther away.

Audio processing

The audio modulates better if it’s conditioned before it’s modulated.
First, the audio should be a fairly high voltage signal. I use an LM 386 low power audio amp IC in front of my XMTR, and it helps boost the audio from my PC sound card.

Next, the audio should be compressed. It helps make the station sound more like the other stations by keeping low volume content from dropping out because the amplitude isn’t adequate to modulate the carrier.

Finally, it should be limited so that certain loud content doesn’t swamp the modulation section and make that icky “it’s turned up too much” sound.

Some XMTRs do all of this internally. Some do none of it. Some do some. What you choose depends on what processing equip you might already have, the bandwidth and average VU level of your content, how much DC power your going to want to pump into the XMTR (All that processing needs addidtional input power), what your personal tastes might be and so on.

RF Buffering

The final stage of the XMTR should buffer the RF output adequately, so that minor changes in the environment around your ANT don’t negatively impact your oscillator and ruin the ANT/XMTR match, etc. Anyone who has fiddled with an unbuffered XMTR will know what I mean – it’s as bad as a VCO.

Here are some transmitter review sites that cover these issues. Always remember that “Net” means Not Entirely True, and draw your own conclusions!

http://www.vintage-radio.com/reviews

www.toddjenkins.com

http://www.geocities.com/raiu_harrison (old, but good)

www.oldtimeradioprograms.com

Previous blogspot article

http://www.part15.us/article

Our reviews

http://www.part15.us/modules.php?name=Reviews