[NLRS] FW: VHF low pass filters?

[Dr. Gerald N. Johnson]

With only high band VHF and UHF TV stations the highpass filter at the 
TV antenna can have a cutoff frequency above 150 MHz and so more easily 
achieve good attenuation at 50.1 MHz.

I take it with channel 2 RF gone that 6m is a lot more practical in the 
twin cities without the adjacent channel TVI and TV splatter across the 
band.

Des Moines has the digital cluster tower a few miles north of the 
existing analog towers at Alleman which are adorned with many other 
antennas. That cluster of towers are 1500 and 2000 feet, big investments 
in feed line and antennas.

I think less than 20 low band VHF stations kept their RF channels nation 
wide. They had to work hard to get the antenna broadbanded and flat 
enough for digital. To say nothing about getting the PA phase linear 
too. Or maybe only the driver because most stations reduced power in 
digital mode. The greater fractional bandwidth made that phase linearity 
way more difficult. I suspect many a temporary UHF digital transmitter 
and antenna was leased, not purchased.

I don't know if its still true but analog IPTV channel 11 and NBC outlet 
WHO-TV channel 13 shared the same feed line and antenna with a big rat 
race hybrid in their shared transmitter building. They are back on their 
analog frequencies. As is KCCI, channel 8.

Channel 8's 2000 foot tower didn't survive construction the first time. 
During a windy storm with freezing rain a big cable block up top got to 
swinging and hit the tower section hard enough it folded the tower.

Another bit of trivia, ISU's WOI AM on 640 uses a tower that was also 
built to hold channel 5 TV (which was also ISU at the time, since been 
sold to a commercial operator) so its more like 5/8 wave than a quarter 
wave. There is only one other 640 station in the country, in San 
Francisco that's considered a clear channel station. For decades WOI had 
to connect a dummy load to the antenna tuner to absorb about 1 KW RF 
because the 5 KW transmitter was only type approved for full power, not 
reduced power and 4 KW was all they could run daytimes and not annoy San 
Francisco. That's changed now, they have another tower to the west of 
the main tower that they switch in at night (before this they were 
daytime only) to put a notch to San Francisco and can also now run the 
same transmitter at reduced power. I don't know what power they run at 
night.

WOI claims to have begun broadcasting about 1917, but that was actually 
the ISU radio club station 9YI sending farm reports on CW or spark, a 
ham activity before commercial messaging was made illegal on ham gear 
and bands.

In those days two letter Y calls were commonly issued to colleges and 
college professors.

73, Jerry, K0CQ

On 1/2/2013 11:00 AM, S. Earl Jarosh wrote:
>
>
>
> The whole digital thing was a cluster from the get go, here is the current
> twin cities channel matrix with the exception that the full HD 45 is now
> dark.  All was suppose to go to UHF then things in the gov happened and
> upper VHF was included.  9 and 11 where allowed to keep their original
> channels at the cutover.  There was suppose to be No low VHF in the Digital
> plan and I did not know Des Moines was allow to keep their old analog
> channel 5 for DTV.  Kind of defeats the purpose of the entire digital
> cluster fix.
>
> Analog Station Network Temp Perm 	Apo 		Dpo
> Tower Loc
> 2 	KTCA 		PBS 	34 	34 	100KW 	924KW 	Shoreview
> East
> 4 	WCCO 		CBS 	32 	32 	100KW 	1000KW 	Shoreview
> West
> 5 	KSTP 		ABC 	50 	35 	100KW 	1000KW 	Shoreview
> West
> 9 	KMSP 		FOX 	26 	9 	316KW 	691KW 	Shoreview
> East
> 11 	KARE 		NBC 	35 	11 	316KW 	774KW 	Shoreview
> West
> 17 	KTCI 		PBS 	16 	26 	141KW 	50KW
> Shoreview East
> 23 	WUCW 		CW 	22 	22 	4570KW 	1000KW 	Shoreview
> West
> 29 	WFTC 		UPN 	21 	29 	5000KW 	1000KW 	Shoreview
> East
> 41 	KPXM 		ION 	40 	40 	2770KW 	1000KW 	Big Lake MN
> 45 	KSTC 		Ind 	44 	45 	5000KW 	82KW  	Shoreview
> West
>
>
> S. Earl Jarosh, N0HZ
> Cell:  612.868.1313
> Off:   763.545.3275
> Home:  763.546.7897
> Fax:   763.546.7897
> earl at moneycenters.com
>
>