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There are 14 messages in this issue.
Topics in this digest:
1a. how do you avoid interfering with fm voice repeaters using the atv f
From: ozsffan
1b. Re: how do you avoid interfering with fm voice repeaters using the a
From: Iain MacDonnell - K6IAM
1c. Re: how do you avoid interfering with fm voice repeaters using the a
From: Ron Wright
1d. Re: how do you avoid interfering with fm voice repeaters using the a
From: ozsffan
1e. Re: how do you avoid interfering with fm voice repeaters using the a
From: James - KB7TBT
2. about the new camcorders
From: ozsffan
3a. Re: how do you avoid interfering with fm voice repeaters using the .
From: a9xw(AT)cs.com
3b. Re: how do you avoid interfering with fm voice repeaters using the .
From: a9xw(AT)cs.com
3c. Re: how do you avoid interfering with fm voice repeaters using the .
From: a9xw(AT)cs.com
3d. Re: how do you avoid interfering with fm voice repeaters using the .
From: ozsffan
3e. Re: how do you avoid interfering with fm voice repeaters using the .
From: ozsffan
4a. Modulators
From: Ray_Vaughan_99
4b. Re: Modulators
From: kevin asato
4c. Re: Modulators
From: Ron Wright
Messages
________________________________________________________________________
1a. how do you avoid interfering with fm voice repeaters using the atv f
Posted by: "ozsffan" ozsffan(AT)yahoo.com ozsffan
Date: Mon Aug 4, 2008 10:10 am ((PDT))
I'm interested in atv, did my research on atv, and found out all the
activity on atv in my area is on 439.25 mhz since that's the only
frequency allowed for it in the most poplar 70 cm band.
And bought a atv transmitter.
Unfortunately, I didn't do any research on fm voice repeaters since I
was interested in atv.
Then I read some hams on the internet saying that atv on 439.25 mhz
is against the law and fcc rulesa everywhere in the U.S.
Then I looked in my arrl repeater directory and seen that most 70 cm
voice repaters are in the 443 mhz segment, right where any amateur tv
transmission will interfere with a bunch of local repeaters at the
same time.
I couldn't find anything in the fcc rules saying it's against the
law to use atv on 439.25 mhz.
Howewver, the people saying it is seem to be going by the fact that
doing so automatically interferes with several fm voice repeaters
at the same time. Which is definitely against the fcc rules.
Who is the genius that decided to put ALL of the 70 centimeter fm
voice repeaters on the ONLY frequency atv is allowed to use in
the ONLY band that is the MOST popular band for atv?
Okay, there are some on the 444 mhz frequencies which isn't any part
of the atv freqency.
However, the 442 and 443 mhz frequencies are.
So how do you avoid causing interference?
Such as transmitting atv and someone then decides to use a fm voice
repeater and can't since most of the fm voice repeaters are on the
ONLY 70 centimeter atv channel in a place where the 70 cm band is
the most popular band for atv.
but is also the most popular 70 centimeter frequencies for fm voice
repeaters.
Messages in this topic (5)
________________________________________________________________________
1b. Re: how do you avoid interfering with fm voice repeaters using the a
Posted by: "Iain MacDonnell - K6IAM" k6iam(AT)dseven.org k6iam
Date: Mon Aug 4, 2008 10:46 am ((PDT))
By whose rules is 439.25 the only allowed frequency for ATV in the 70cm
band?? The ARRL band-plan shows 427.25 (happens to be cable channel 58)
as the simplex ATV frequency. Other possibilities are 421.25, 426.25 and
434.00.
~Iain / K6IAM
ozsffan wrote on 08/04/08 09:55:
> >
> >
> > I'm interested in atv, did my research on atv, and found out all the
> > activity on atv in my area is on 439.25 mhz since that's the only
> > frequency allowed for it in the most poplar 70 cm band.
> >
> > And bought a atv transmitter.
> >
> > Unfortunately, I didn't do any research on fm voice repeaters since I
> > was interested in atv.
> >
> > Then I read some hams on the internet saying that atv on 439.25 mhz
> > is against the law and fcc rulesa everywhere in the U.S.
> >
> > Then I looked in my arrl repeater directory and seen that most 70 cm
> > voice repaters are in the 443 mhz segment, right where any amateur tv
> > transmission will interfere with a bunch of local repeaters at the
> > same time.
> >
> > I couldn't find anything in the fcc rules saying it's against the
> > law to use atv on 439.25 mhz.
> >
> > Howewver, the people saying it is seem to be going by the fact that
> > doing so automatically interferes with several fm voice repeaters
> > at the same time. Which is definitely against the fcc rules.
> >
> > Who is the genius that decided to put ALL of the 70 centimeter fm
> > voice repeaters on the ONLY frequency atv is allowed to use in
> > the ONLY band that is the MOST popular band for atv?
> >
> > Okay, there are some on the 444 mhz frequencies which isn't any part
> > of the atv freqency.
> >
> > However, the 442 and 443 mhz frequencies are.
> >
> > So how do you avoid causing interference?
> >
> > Such as transmitting atv and someone then decides to use a fm voice
> > repeater and can't since most of the fm voice repeaters are on the
> > ONLY 70 centimeter atv channel in a place where the 70 cm band is
> > the most popular band for atv.
> >
> > but is also the most popular 70 centimeter frequencies for fm voice
> > repeaters.
> >
> >
Messages in this topic (5)
________________________________________________________________________
1c. Re: how do you avoid interfering with fm voice repeaters using the a
Posted by: "Ron Wright" mccrpt(AT)verizon.net lt_wright_flg
Date: Mon Aug 4, 2008 11:26 am ((PDT))
439.25 is not the only freq that can be used for ATV on 420-450.
Due to no repeaters on 431-433 and 435-438 439.25 was chosen assuming
one had the standard 1.25 MHz lower side band and 4.5 MHz upper side
band, the standard NTSC TV signal.
However, this is not the case for most ATV rigs simply modulate the
final or driver with little filtering to get rid of most of the LSB.
Repeaters typically use the lower part of 420 for output and
439.25 input. So 439.25 became popular.
Still it is difficult to keep the 420 range repeater output out of
the 439 input.
Some use split sites, some use seperate antennas and some use
interdigital filters, but due to wide band it is a pain.
The problem with 439.35 its bandwidth of 4.5 MHz really is using 439.25
up to 443.75 where much of the FM repeater outputs are.
You can use 420-430 for ATV.
73, ron, n9ee/r
73, ron, n9ee/r
> >From: ozsffan <ozsffan(AT)yahoo.com>
> >Date: 2008/08/04 Mon PM 12:55:31 EDT
> >To: Ham-ATV(AT)yahoogroups.com
> >Subject: [Ham-ATV] how do you avoid interfering with fm voice
repeaters using the atv frequency?
> >
> >I'm interested in atv, did my research on atv, and found out all the
> >activity on atv in my area is on 439.25 mhz since that's the only
> > frequency allowed for it in the most poplar 70 cm band.
> >
> >And bought a atv transmitter.
> >
> >Unfortunately, I didn't do any research on fm voice repeaters since I
> > was interested in atv.
> >
> >Then I read some hams on the internet saying that atv on 439.25 mhz
> > is against the law and fcc rulesa everywhere in the U.S.
> >
> >Then I looked in my arrl repeater directory and seen that most 70 cm
> >voice repaters are in the 443 mhz segment, right where any amateur tv
> >transmission will interfere with a bunch of local repeaters at the
> >same time.
> >
> >I couldn't find anything in the fcc rules saying it's against the
> >law to use atv on 439.25 mhz.
> >
> >Howewver, the people saying it is seem to be going by the fact that
> >doing so automatically interferes with several fm voice repeaters
> > at the same time. Which is definitely against the fcc rules.
> >
> >Who is the genius that decided to put ALL of the 70 centimeter fm
> > voice repeaters on the ONLY frequency atv is allowed to use in
> >the ONLY band that is the MOST popular band for atv?
> >
> >Okay, there are some on the 444 mhz frequencies which isn't any part
> > of the atv freqency.
> >
> >However, the 442 and 443 mhz frequencies are.
> >
> >So how do you avoid causing interference?
> >
> >Such as transmitting atv and someone then decides to use a fm voice
> >repeater and can't since most of the fm voice repeaters are on the
> >ONLY 70 centimeter atv channel in a place where the 70 cm band is
> > the most popular band for atv.
> >
> >but is also the most popular 70 centimeter frequencies for fm voice
> > repeaters.
> >
> >
Ron Wright, N9EE
727-376-6575
MICRO COMPUTER CONCEPTS
Owner 146.64 repeater Tampa Bay, FL
No tone, all are welcome.
Messages in this topic (5)
________________________________________________________________________
1d. Re: how do you avoid interfering with fm voice repeaters using the a
Posted by: "ozsffan" ozsffan(AT)yahoo.com ozsffan
Date: Mon Aug 4, 2008 5:19 pm ((PDT))
> > You can use 420-430 for ATV.
Not according to FCC rules.
Messages in this topic (5)
________________________________________________________________________
1e. Re: how do you avoid interfering with fm voice repeaters using the a
Posted by: "James - KB7TBT" kb7tbt(AT)gmail.com kb7tbt
Date: Mon Aug 4, 2008 7:43 pm ((PDT))
Where are you and where is this rule you are speaking of?
In the USA 420 - 440 is allocated for many things including ATV
specifically 421.25 aka Cable CH 57
James
KB7TBT
NEGARC Activities Manager
www.kb7tbt.com
www.ne4ga.org
www.myspace.com/kb7tbt
>> >> You can use 420-430 for ATV.
> >
> > Not according to FCC rules.
> >
> >
Messages in this topic (5)
_____________________________________________________________________
_____________________________________________________________________
2. about the new camcorders
Posted by: "ozsffan" ozsffan(AT)yahoo.com ozsffan
Date: Mon Aug 4, 2008 10:26 am ((PDT))
I hope my previous message didn't sound like I'm angry. I'm not.
That sometimes happens with text where you can't hear the tone of
the person's voice.
Another reason atv is better. ;)
Altough I do think several atv sites need updating.
While researching, several sites said any camcorder (old or new) with
a/v outputs will work for atv.
Since I didn't have a camcorder, I looked for old ones,couldn't find
any, so ended up buying a brand new camcorder.
which I made sure had a/v outputs.
Only to find out that all of the new camcorders at consumer level
automatically disable the live picture whenever the audio/video
jacks are plugged in to them.
They also disable the recording function when the a/v jacks are
plugged in.
Only pre-recorded material is able to be transmitted over them on
atv.
And I wanted to do two way communication using pictures with them.
(impossible)
Since this is the "standard" today for new camcorders, you need either
an old camcorder that will still allow live pictures to be shown
when the a/v cords are hooked up to it or a camera designed for
amateur tv use. or some other camera.
My point is the new camcorders aren't any good for atv use unless
all you want to do with them is to transmit pre-recorded material
over atv.
At least, that's been my experience.
As soon as I can get one that does live pictures with the cam plugged
into my atv transmitter, instead of only pre-recorded material, I'm
looking forward to being more active in atv.
Messages in this topic (1)
____________________________________________________________________
____________________________________________________________________
3a. Re: how do you avoid interfering with fm voice repeaters using the .
Posted by: "a9xw(AT)cs.com" a9xw(AT)cs.com
Date: Mon Aug 4, 2008 10:54 am ((PDT))
ATV operates on 421.25, 426.25, 427.25, 439.25 and a few odd frequencies
inbetween. It is not in the rules, it is in the band plan, local
coordination and the spirit to avoid interference between users.
Likewise most ATV is horizontal (California being Vertical because
that is what they decided decades ago)
while FM is nearly all vertical to provide cross pol signal rejection
to improve interference margins.
Henry AA9XW </HTML>
Messages in this topic (5)
_____________________________________________________________________
3b. Re: how do you avoid interfering with fm voice repeaters using the .
Posted by: "a9xw(AT)cs.com" a9xw(AT)cs.com
Date: Mon Aug 4, 2008 11:41 am ((PDT))
439.25 was chosen decades ago because ATV and weak signal used to share 432.
ATV moved off to 439.25 to avoid having sidebands in the "weak signal" window
of 431-433. We're talking the 1950's folks when that was set up.
AA9XW </HTML>
Messages in this topic (5)
______________________________________________________________________
3c. Re: how do you avoid interfering with fm voice repeaters using the .
Posted by: "a9xw(AT)cs.com" a9xw(AT)cs.com
Date: Mon Aug 4, 2008 11:43 am ((PDT))
It has long been shows that TV only rarely interferes with FM, the
opposite is trtue 100% of the time becuase of the wide receiver
bandwidth of TV vs the very narrow bandwidth of FM. Many now use
Lower VSB on 439.25 with regular VSB on 421.25.
Any inband repeater is going to need filters to prevent IM, desense
and sidebands must be kept inside the ham band (to -29 dbc)
AA9XW </HTML>
Messages in this topic (5)
____________________________________________________________________
3d. Re: how do you avoid interfering with fm voice repeaters using the .
Posted by: "ozsffan" ozsffan(AT)yahoo.com ozsffan
Date: Mon Aug 4, 2008 5:06 pm ((PDT))
--- In Ham-ATV(AT)yahoogroups.com, a9xw(AT)... wrote:
> >
> > ATV operates on 421.25, 426.25, 427.25, 439.25 and a few odd
frequencies
> > inbetween. It is not in the rules, it is in the band plan, local
coordination and
Thsnks, but just to clarify, I'm in the U.S. north of line A and
according to FCC rules, ham transmissions are not allowed at all from
420 mhz to 430 mhz.
no matter what mode it is.
Which leaves the only legal 70cm atv (with audio) frequency as
439.25 mhz.
Which is why all the atv activity here is or was on 439.25 mhz.
Here, 420 mhz to 430 mhz are used by several police departments.
Messages in this topic (5)
_____________________________________________________________________
3e. Re: how do you avoid interfering with fm voice repeaters using the .
Posted by: "ozsffan" ozsffan(AT)yahoo.com ozsffan
Date: Mon Aug 4, 2008 5:16 pm ((PDT))
--- In Ham-ATV(AT)yahoogroups.com, a9xw(AT)... wrote:
> >
> > Ithas long been shows that TV only rarely interferes with FM, the
opposite is
> > trtue 100% of the time becuase of the wide receiver bandwidth of TV
vs the
> > very narrow bandwidth of FM.
Thanks. I didn'trealize that TV only rarely interferes with FM.
Now I know thanks to the posts here.
Many now use Lower VSB on 439.25 with regular VSB
> > on 421.25.
It's against FCC rules for me to tramsmit anything on 421.25 mhz from
here.
Any inband repeater is going to need filters to prevent IM, desense
> > and sidebands must be kep inside the ham band (to -29 dbc)
> >
> > AA9XW </HTML>
> >
> >
> > [Non-text portions of this message have been removed]
> >
Messages in this topic (5)
_____________________________________________________________________
_____________________________________________________________________
4a. Modulators
Posted by: "Ray_Vaughan_99" ray(AT)rayvaughan.com ray_vaughan_99
Date: Mon Aug 4, 2008 6:03 pm ((PDT))
Just a suggestion. As I'm sure everyone knows, Analgo NTSC in the US
is going dark in the US next year (unless voters demand a delay). The
publics loss is our gain!
Keep an eye out for Cable TV grade modulators on the used market.
These are already common at hamfests for somewhere around $100. Many
are frequency agile. As long as they go up to 440 MHz, CATV WW or 59,
they could be exciter for your ATV project. CATV means the lower
sideband IS suppressed enough to reuse the lower channel for something
else. With this equipment being so cheap I don't see a good reason to
waste spectrum with a modulator that doesn't suppress the lower sideband.
The output of most good ones will be about 60 dBmV. That translates
to 1 VRMS or 13 mV at 75 ohms. You will have to consider the
conversion from 75 to 50 ohms if you're going to amplify it with an
amp with 50 ohm input.
http://www.maxim-ic.com/appnotes.cfm/appnote_number/808
There are also a lot of single channel mods out there too. For many
years I used Scientific Atlanta equipment, like the 6350. They're
very modular so you can easily do things like modify the IF if you
need to. Don't be surprised if you see letters on the two right
modules. Here's the data on the channels you want:
Ch Edges Video Audio Color
57 (UU) 420-426 421.25 425.75 424.83
58 (VV) 426-432 427.25 431.75 430.83
59 (WW) 432-438 433.25 437.75 436.83
So if you need Ch 58, look for "VV" on the modules.
Since the cost isn't much different, I would look for an agile unit.
If you can find a deal on a good modulator, I think you'll find the
video quality to be far better and more stable than any of the amateur
grade ATV Transmitters.
Another suggestion related to be Analog shut down. Low Power TV
stations don't have to go digital only when the big guys do, but I
suspect many Analog transmitters will go on the market. They won't
have a market in Broadcasting any more. A 1 kW TV transmitter is a
good sized equipment rack with one heck of a blower on it. It would
also likely use 3 phase power. I would suggest to think smaller and
look for a solid state 10 or 100 W LPTV UHF transmitter. Major
retuning WILL be needed, including some parts changes. But in theory,
a low UHF (14-20) transmitter might make it to our ATV band.
Just some ideas to trigger a discussion.
Thanks
Ray, KD4BBM
Messages in this topic (3)
___________________________________________________________________
4b. Re: Modulators
Posted by: "kevin asato" kc6pob(AT)yahoo.com kc6pob
Date: Mon Aug 4, 2008 6:31 pm ((PDT))
Oh, no. Not another, "We're not ready. Can we have another delay".
We've already been through one drop dead date! I've looked at some of
the changeovers for Los Angeles and a a few stations
(secondary and 3rd tier, not network) are going to go with a flash
cut with due dates on the 17th.
Agreed, after that time, we will probably see a fire sale for all
sorts of analog equipment.
kevin
kc6pob
Just a suggestion. As I'm sure everyone knows, Analgo
NTSC in the US is going dark in the US next year
(unless voters demand a delay). The
publics loss is our gain!
Messages in this topic (3)
_________________________________________________________________
4c. Re: Modulators
Posted by: "Ron Wright" mccrpt(AT)verizon.net lt_wright_flg
Date: Mon Aug 4, 2008 8:12 pm ((PDT))
Cable TV does not have to go HDTV in Feb, only the over the air
stations. I don't see much change in cable except for the upgrade
to digital, not HD, but whatever format a cable company chooses.
Might see demods on the market since the cable companies that get
their over the air channels have to go to converter boxes.
Most of our cable companies get the local stations via a direct
fiber feed.
The TV transmitter can die and we cable subscribers still get
the station.
73, ron, n9ee/r
> >From: Ray_Vaughan_99 <ray(AT)rayvaughan.com>
> >Date: 2008/08/04 Mon PM 09:03:33 EDT
> >To: Ham-ATV(AT)yahoogroups.com
> >Subject: [Ham-ATV] Modulators
> >
> >Just a suggestion. As I'm sure everyone knows, Analgo NTSC in the US
> >is going dark in the US next year (unless voters demand a delay). The
> >publics loss is our gain!
> >
> >Keep an eye out for Cable TV grade modulators on the used market.
> >These are already common at hamfests for somewhere around $100. Many
> >are frequency agile. As long as they go up to 440 MHz, CATV WW or 59,
> >they could be exciter for your ATV project. CATV means the lower
> >sideband IS suppressed enough to reuse the lower channel for something
> >else. With this equipment being so cheap I don't see a good reason to
> >waste spectrum with a modulator that doesn't suppress the lower sideband.
> >
> >The output of most good ones will be about 60 dBmV. That translates
> >to 1 VRMS or 13 mV at 75 ohms. You will have to consider the
> >conversion from 75 to 50 ohms if you're going to amplify it with an
> >amp with 50 ohm input.
> >http://www.maxim-ic.com/appnotes.cfm/appnote_number/808
> >
> >There are also a lot of single channel mods out there too. For many
> >years I used Scientific Atlanta equipment, like the 6350. They're
> >very modular so you can easily do things like modify the IF if you
> >need to. Don't be surprised if you see letters on the two right
> >modules. Here's the data on the channels you want:
> >
> >Ch Edges Video Audio Color
> >57 (UU) 420-426 421.25 425.75 424.83
> >58 (VV) 426-432 427.25 431.75 430.83
> >59 (WW) 432-438 433.25 437.75 436.83
> >
> >So if you need Ch 58, look for "VV" on the modules.
> >
> >Since the cost isn't much different, I would look for an agile unit.
> >
> >If you can find a deal on a good modulator, I think you'll find the
> >video quality to be far better and more stable than any of the amateur
> >grade ATV Transmitters.
> >
> >Another suggestion related to be Analog shut down. Low Power TV
> >stations don't have to go digital only when the big guys do, but I
> >suspect many Analog transmitters will go on the market. They won't
> >have a market in Broadcasting any more. A 1 kW TV transmitter is a
> >good sized equipment rack with one heck of a blower on it. It would
> >also likely use 3 phase power. I would suggest to think smaller and
> >look for a solid state 10 or 100 W LPTV UHF transmitter. Major
> >retuning WILL be needed, including some parts changes. But in theory,
> >a low UHF (14-20) transmitter might make it to our ATV band.
> >
> >Just some ideas to trigger a discussion.
> >
> >Thanks
> >
> >Ray, KD4BBM
> >
> >
Ron Wright, N9EE
727-376-6575
MICRO COMPUTER CONCEPTS
Owner 146.64 repeater Tampa Bay, FL
No tone, all are welcome.
------------------------------------------------------------------
*******************************************************************
ABOVE IS A CROSS POST TO THE PACKET RADIO NETWORK IN AN EFFORT TO
PROMOTE FURTHER INTEREST IN SLOW SCAN TELEVISION AND PACKET RADIO
Courtesy Tony VK7AX VK7AX(AT)VK7AX.#ULV.TAS.AUS.OC
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