• Get involved.
    We want your input!
    Apply for Membership and join the conversations about everything related to broadcasting.

    After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
    If you use a disposable or false email address, your registration will be rejected.

    After your membership is approved, please take a minute to tell us a little bit about yourself.
    https://www.radiodiscussions.com/forums/introduce-yourself.1088/

    Thanks in advance and have fun!
    RadioDiscussions Administrators

Rangemaster and LPAM

D

dbdigital

Guest
It's been a while since I've looked at the Rangemaster website and while viewing it yesterday, I noticed Keith made a few changes concerning frequency requirements.

In the past, he only recommended using channels in the expanded band (and still recommends 1610 and 1620 as the best) but now he is offering crystals for 1590 and 1600 and recommends that the Rangemaster not be used on channels below 1400. Apparently, channels 1400 and up are acceptable. Did Keith change the design of his TX or will range be decreased if the Rangemaster is used below the X-Band?

On a related topic, I think the framers of the LPAM proposal made a mistake by not suggesting that the service be allowed to use any open channel in the AM band instead of confining it to the X-Band. Where I live, there are no open channels in the X-Band thanks to the TIS stations in the area. However, using the BC Map program, I noticed that there are a few open channels lower in the band which could be used for a local AM service in my city.

Should the day come (if ever) that the FCC seriously considers LPAM, I hope they will remove the X-Band stipulation.

db
 
DB:

Keith has always offered crystals for frequencies below 1610 but usually they had to be special ordered.

The primary reason Keith (or any of us that sell the Rangemaster) don't recommend a frequency below 1400 is that the range of the transmitter is greatly reduced at lower frequencies in the AM band. Channels above 1500 deliver the best range.

As one one of the creators of the LPAM Petition (RM-11287) I can give you a very valid reason why we only considered using the X band for the proposed service. Among the vast majority of broadcast engineers is the misconception that the AM band is already too crowded and no room exists for any additional stations regardless of their power level. Both you and I (and millions of other people) knows this to be false, especially in rural areas and small cities that exist well away from metro areas. In any event, it will be possible with engineering practices to prove the X band is not too crowded and can handle additional stations of modest power levels. Perhaps, if we get this service passed, it may be possible to expand it to the lower end of the band at some point. When I lived in northern Maine it was apparent you could fit a couple dozen stations on the AM dial in that region simply because there were only about half a dozen AM stations serving an area the size of Connecticut and Rhode Island combined.
 
William C. Walker said:
DB:

Keith has always offered crystals for frequencies below 1610 but usually they had to be special ordered.

The primary reason Keith (or any of us that sell the Rangemaster) don't recommend a frequency below 1400 is that the range of the transmitter is greatly reduced at lower frequencies in the AM band. Channels above 1500 deliver the best range.

As one one of the creators of the LPAM Petition (RM-11287) I can give you a very valid reason why we only considered using the X band for the proposed service. Among the vast majority of broadcast engineers is the misconception that the AM band is already too crowded and no room exists for any additional stations regardless of their power level. Both you and I (and millions of other people) knows this to be false, especially in rural areas and small cities that exist well away from metro areas. In any event, it will be possible with engineering practices to prove the X band is not too crowded and can handle additional stations of modest power levels. Perhaps, if we get this service passed, it may be possible to expand it to the lower end of the band at some point. When I lived in northern Maine it was apparent you could fit a couple dozen stations on the AM dial in that region simply because there were only about half a dozen AM stations serving an area the size of Connecticut and Rhode Island combined.
Click to expand...

Hey, William. Long time, no hear from. Hope all is well. Don't be a stranger.

As I read your explanation, there would be fewer objections and a greater chance of the petition being accepted if the service were confined to the X-Band. Where I live, CalTrans has taken over 1610 for construction delay warnings but they hardly ever use it. And only a few TIS stations broadcast continually.

This is the kind of waste I wish the FCC would eliminate.

db
 
Unfortunately it shows patterns, not contours, which would be much more useful. The pattern is the general shape of the radiation, while contours would actually show signal strengths. Most useful would be 0.5 and 0.025 mv/m which are protected and interfering contours. One could then make a good estimate of where an open AM channel existed.
 
wkbam1690 said:
Unfortunately it shows patterns, not contours, which would be much more useful. The pattern is the general shape of the radiation, while contours would actually show signal strengths. Most useful would be 0.5 and 0.025 mv/m which are protected and interfering contours. One could then make a good estimate of where an open AM channel existed.
Click to expand...

This is true and I meant to say patterns, not contours. But the program can still be useful as a preliminary step in determining if a channel could possibly be open and from there researched in more detail.

db
 
Regardless, this is a very useful program!
Thanks for pointing it out, db!
 
wkbam1690 said:
Unfortunately it shows patterns, not contours, which would be much more useful.
Click to expand...

The field strength contours shown at http://www.radio-locator.com/ include both the radiation pattern of the antenna system itself, and the effects of ground conductivity on the field contours for that radiation pattern.
//
 
On the "other" board, one poster reports a significant improvement in coverage using two Rangemasters. In this configuration he has them mounted on the same pole, same height. However, one TX is mounted right side up and the other mounted upside down. They're both tuned and synced, of course.

Another poster stated that the FCC does not like to see Part-15 TX's mounted that close together. This may be true, but I can find no ruling giving a distance requirement between transmitters.

Does the FCC have a rule for distance between Part-15 transmitters?

db
 
dbdigital said:
On the "other" board, one poster reports a significant improvement in coverage using two Rangemasters. In this configuration he has them mounted on the same pole, same height. However, one TX is mounted right side up and the other mounted upside down. They're both tuned and synced, of course.

Another poster stated that the FCC does not like to see Part-15 TX's mounted that close together. This may be true, but I can find no ruling giving a distance requirement between transmitters.

Does the FCC have a rule for distance between Part-15 transmitters?

db
Click to expand...
No.
 
SUPERCASTER said:
dbdigital said:
On the "other" board, one poster reports a significant improvement in coverage using two Rangemasters. In this configuration he has them mounted on the same pole, same height. However, one TX is mounted right side up and the other mounted upside down. They're both tuned and synced, of course.

Another poster stated that the FCC does not like to see Part-15 TX's mounted that close together. This may be true, but I can find no ruling giving a distance requirement between transmitters.

Does the FCC have a rule for distance between Part-15 transmitters?

db
Click to expand...
No.
Click to expand...

I didn't think so. Thanks.

db
 
Desert Ear said:
Where's the "other" board?

I'd like to see the details about an upside down Rangemaster!
Click to expand...

As I understand it, posters here are not permitted to provide a link to the other board.

Here is the thread:

"Right now, I am experimenting in some sites with one Rangemaster right side up and one upside down on the same pole. FYI- just for short term testing. Signal is improved though.

The Rangemaster has 2 jumper settings to set phase. Not sure why it increasing our signal- it just is.

I assumed there would be lobes- but so far nothing. As you may know, they are synched on the same crystal.

Audio input on both units are maxed out and controlled from the processing in the studio. I assumed it would equal the distribution.

What would you suggest in using two or three transmitters on the same crystal? I have no distortion (that is apparent) and the signal has improved in all directions- that I can tell.

My ground lead is a number 2 thick cable running to two 8 foot ground rods and a 4 foot ground rod.

The transmitters are exactly the same height on the pole except one is pointing down.

What would you think about running one transmitter horizonally and one vertically?

The phase is actually two rows of jumper positions and they control the RF phase.

Seems to be sending a pretty good signal out. I just tried turning off the upside down transmitter and the signal worsened in all directions. (Yes- I retuned the transmitter as well)"

db
 
Have you considered simply grounding the two Rangemaster transmitters to each other (just connecting their two grounding posts with a short, heavy jumper wire)?

Sometimes AM equipment unexpectedly works better when odd things are tried. Back when this board had pink lettering on a black background (quite a while ago!), I recall that someone posted about using a 2' or so rigid wire counterpoise connected to a Talking House www.talkinghouse.com outdoor ATU/8.5' whip antenna system's grounding post at a 45 degree angle. Much to his surprise, it almost doubled his transmitter's range. (I'm guessing that the counterpoise improved the capacitive RF coupling to the mast and/or to other nearby grounded metal objects.)


-- Black Shire
 
There are many more full power stations below 1600, it makes night range more difficult. Gererally Part 15 AM lives in the high band when possible.
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom