• 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

Increase Signal Range of AM Station

C

ChiefOperator

I met the owner of a 1kW directional AM that asked me whether I could do anything to extend the range of his signal.

The station is running an older analog Inovonics processor and the modulation is all over the place. I have no doubt that I could increase the range through aggressive processing. This leads to my question: I would rather not reinvent the wheel. Undoubtably there are many here who have faced the same issue. What did you do and how successfull was the fix? Did you use just one processor or chain a couple boxes together? I'll take all suggestions from anyone who has been successful in this area.

Thanks!
 
I run into a lot of station where the ground system is 30-40 years old and basically non-existent. Replacing the ground system is a lot of money, but it can have amazing results. Aggressive processing might just be a band-aid on a broken leg.

If the ground system is not the problem, then I will have to punt the ball...
 
ChiefOperator said:
Thanks Lazy J-

No, talking with the other engineer, the ground system and entire system in general is fine.
Click to expand...

Then he's stuck with what he has. I'm guessing he's a Class C on a local channel and he's fighting all other Cs.
 
I recently replaced a Inovonics 235 with an Omnia One on a 5kw solid state AM - no other changes were made. The station immediately picked up coverage in the fringe area.

Just my experience... YMMV...

RFB
 
I think there are several questions that need to be addressed in my opinion before any advice can be given. First are you sure the processing is the problem? Has the coverage degraged or changed over time? Does the efficiency of the transmitter looks right for the licensed common point currrent? Since you state it's a directiional operation what do the monitor points looks like over time? Have any dropeed or changed substantially? Also you might look at the origianl proof of the DA and do a partial proof to compare present day performance. Are your coverage expectations realistic? i.e. if you expect a 1kw on a high in the band frequency, where the ground conductivity is 4mho's to serve areas 20 miles or more away it's not going to happen. Realistic listenable coverage is only going out to about the 2 to 5 mv/m contour, more or less depending on interference levels. Good processing can help a signal but don't expect processing to be a cure all for other deficiencies. In todays world a 1kw daytime, above say 1100 KHz or so with a quarter wave stick, is lucky to serve an area 15 to 20 miles from the transmitter with a solid signal to most receivers.
 
Thank you all for the replies. I understand that there are many issues that determine coverage and, of course, all those will be evaluated. However, I wished to focus on processing mostly because I noted that the older processor was doing a poor job controlling audio levels and, as I mentioned before, the modulation was all over the place.

If I recall, some have mentioned that they have had success using various processing, including chaining boxes. I hope to hear some of those "formulas" so that I can experiment some.

Thanks..
 
Just buy an Omnia ONE AM, and see what it does. Most cost effective start to solve coverage problems. Chaining a bunch of boxes is for old top 40 PD's from the '70's with a big budget who like to tinker.

Then you can explore---transmitter--can you modulate it? Antenna/ground system--is there a problem there? --all of which potentially much more costly to remedy.
 
I agree. You know the modulation isn't as good as it can be. If your engineering guy has already checked some radials and things seem OK, chances are they are ok. Does your common point, phases, or base currents change much from wet to dry soil? If they don't change much, chances are the ground system is OK. Try the Omnia One or another decent AM processor. To be honest, the newer Inovonics processor sounds pretty good. I have it on a station and have been very happy with the results. Either way, I think you'll be well suited by a new processor.
 
Processing has come a long way since the days of the analog Inovonics box, and a little money spent on a good processor will go a long way. If you split your budget among several different units with the intentions of "chaining" them all together, I think you will end up with a far inferior and disappointing result than if you were to invest the entire budget in one good processor. If the studio and transmitter are co-located, one box is all you need. If you have an STL, then an additional processor to perform AGC and limiting is good practice, but let the box at the transmitter do all the rest.

Call your favorite supplier (BGS, SCMS, BSW, etc.) and ask to arrange for a demonstration of a processor of your choice. Orban, Omnia, and Vorsis are the most prevalent names, and all have excellent AM units at different price levels. Almost all suppliers/manufacturers will let you try before you buy.

Just don't get so aggressive on the processing that you drive listeners away. My radios have a volume control where I can turn the volume up or down, but there's no adjustment for cruddy audio. Being competitive is one thing, but being fatiguing is another.
 
The most common mistakes at bad sounding AM stations are usually:
1. high negative modulation
2. rotation and bandwidth problems with ATU's, etc

Poor coverage is almost always related to ground systems rather than low modulation
 
With all due respect, I don't think there has been enough information provided to say that a new processor is the answer to the problem(s).
A new processor can certainly improve the sound of a facility, but it can also make a bad situation worse. If the transmitter has tilt and overshoot problems in the modulator you can blow up the rig with the dense modulation provided by a modern processor. If the antenna system bandwidth is poor you may have similar problems or a Vswr fold back or trips due to the transmitter being unhappy with the high modulation levels into a poor load. (How is running at reduced power going to help coverage?)
In addition to the previous qusetions, it would help a lot if you could tell us if this is an older plate mod tube rig or a newer solid state transmitter. What frequency and how old is the design of the phasor and ATU's? What is the current processing?
Without this info, it seems to me, this would be like calling a doctor and telling him you have high blood pressure and then asking what kind of bypass surgery you need without an exam or diagnostic tests.
A new processor may help the situation but it could make things worse. You are asking someone to spend 3300 dollars (possibly the entire yearly engineering budget or more) on something that may or may not be the cure.
 
vacuum tube is absolutely correct.

More information is needed. What is the age and condition of the transmitter? Have you measured the sideband response of the antenna system?
 
Is this station directional day/night, or night only?
 
vacuum tube said:
With all due respect, I don't think there has been enough information provided to say that a new processor is the answer to the problem(s).
A new processor can certainly improve the sound of a facility, but it can also make a bad situation worse. If the transmitter has tilt and overshoot problems in the modulator you can blow up the rig with the dense modulation provided by a modern processor. If the antenna system bandwidth is poor you may have similar problems or a Vswr fold back or trips due to the transmitter being unhappy with the high modulation levels into a poor load. (How is running at reduced power going to help coverage?)
In addition to the previous qusetions, it would help a lot if you could tell us if this is an older plate mod tube rig or a newer solid state transmitter. What frequency and how old is the design of the phasor and ATU's? What is the current processing?
Without this info, it seems to me, this would be like calling a doctor and telling him you have high blood pressure and then asking what kind of bypass surgery you need without an exam or diagnostic tests.
A new processor may help the situation but it could make things worse. You are asking someone to spend 3300 dollars (possibly the entire yearly engineering budget or more) on something that may or may not be the cure.
Click to expand...

I absolutely agree. I think you’re starting at the wrong end. Your first tool should not be a new processor, it should be a signal strength meter and the original proof. Then investigate the transmitter operation and the antenna bandwidth. Otherwise, as someone said, you mayl only be putting a band-aid on things and it may in fact make things worse.
 
Here's a nasty little trick I've recently figured out. If you're at above 1000khz and you know some hams, check around and see if one of them has a AEA HF SWR Antenna Analyst you could borrow. I've been playing with one I bought at a hamfest. It draws nice curves of your bandwidth. I was a bit supprised to see how several of the stations I play with were a bit skewed on on side or the other. It's a eye opener. Of course the best thing would be a nice network analyzer and the associated amp and return loss bridge of course.
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom