[BC] lpfm question

[Broadcast List USER]

There is a generally accepted rule of thumb regarding FM power.  Of  
course, a rule of thumb is just that, and is not any replacement for  
actually doing real Engineering.

But the rule of thumb is move as high as you can get and still  
maintain at least 20,000 Watts ERP.

Of course, this doesn't work for either Class A or LPFM stations.  In  
general, Class A (and LPFM) stations should to to the maximum height  
for the Class, at maximum power.

UNLESS you only want mobile listeners.  Then, since you don't have to  
worry about building penetration, you can greatly reduce ERP.  If you  
are in some small town with only one story wood framed buildings,  
lower power and more height would work.

Also, as others have stated in different ways, the fewer bays and the  
greater transmitter power, the better.  The Class As I have built  
have been either three-bay half-wave spaced (a good compromise), or  
just two bays, half-wave spaced.  Were I to build a LPFM, I would  
either put up one bay, or if the antenna was very close to people,  
two bays at half-wave spacing.

The fewer the number of bays, the fewer minima and minor lobes.  A  
fat main lobe is a great thing.

On Feb 19, 2009, at 3:24 PM, broadcast-request at radiolists.net wrote:

> From: ChuxGarage at aol.com
>
> LPFM stations can be over 100 ft HAAT, but the trade off is you  
> must run at
> lower power to compensate. There is no free lunch.  It is possible  
> in some
> circumstances that running, say 125 ft HAAT and about 75 watts ERP  
> might be a
> better compromise.  There are lots of variables which are a little  
> difficult to
> predict on a news board.
>
> Chuck Conrad
>
> In a message dated 2/19/2009 5:00:43 AM Central Standard Time,
> broadcast-request at radiolists.net writes:
>>
>>  Not to be rude but 100 watts ERP at 100 feet I thought was the MAX
>> for an LPFM... Mine is at 60 feet....