-
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
Another Question about HD Radio
- Thread starter jras20
- Start date
M
Mediafrog
Guest
> When they hookon the HD to the Missouri City main stick, do
> they half to put up another antenna? or can they broadcast
> it onto the same antenna?
Last word on this board was that the Senior Road Tower HD conversion project had been delayed until September. New master antenna, new combiner, new transmitters. Anyone have more details and/or an update?
> they half to put up another antenna? or can they broadcast
> it onto the same antenna?
Last word on this board was that the Senior Road Tower HD conversion project had been delayed until September. New master antenna, new combiner, new transmitters. Anyone have more details and/or an update?
J
j_u_a_n
Guest
> > When they hookon the HD to the Missouri City main stick,
> do
> > they half to put up another antenna? or can they
> broadcast
> > it onto the same antenna?
>
> Last word on this board was that the Senior Road Tower HD
> conversion project had been delayed until September. New
> master antenna, new combiner, new transmitters. Anyone have
> more details and/or an update?
>
Another quick question: Who is paying for all this?
> do
> > they half to put up another antenna? or can they
> broadcast
> > it onto the same antenna?
>
> Last word on this board was that the Senior Road Tower HD
> conversion project had been delayed until September. New
> master antenna, new combiner, new transmitters. Anyone have
> more details and/or an update?
>
Another quick question: Who is paying for all this?
C
CW
Guest
> When they hookon the HD to the Missouri City main stick, do
> they half to put up another antenna? or can they broadcast
> it onto the same antenna?
They could if the antenna could take the extra power and/or the digital input....Digital stations are at 1% of the analog TPO (Transmitter power out) so for the 9 stations there, adding digital in one method which I think they will use will require new combiners and a second feed to the antenna....the antenna (a Harris/now Dielectric Cavity Back Resonator or CBR panel) does not have the second port for the digital feed as it was installed and modified from the 1980s till present. Thus a new antenna will have to be installed or at least new input ports along with a second feedline to the digital inputs (which will be left hand circular polarized).
There are several ways to do IBOC on FM...One way is low level combining where the two exciters (at low power) are combined and then amplified by a common linear amplifier...and then on to one antenna...BUT the amplifier in current FM analog transmitters are Class C Mode (not to be confused to a Class C FM station). A class C amp is non linear and is only good for FM and other non AM signals. Thus all new xmtrs must be installed...a lot of cash!
The other methods are high level combining.
1) Use same FM analog xmtr and add digital xmtr using coupler...analog xmtr must run higher power than it does now....if not, time for a new FM analog xmtr...more money....also coupler DUMPS the added power (due to the coupling) into a dummy load....HEAT is wasted RF and dummy load is needed..more money..
digital xmtr must be running 10x needed power...and that extra power is also dumped into the dummy load...thus lots of heat...and increased cooling if dummy load is in same room...plus the heat of the digital xmtr (not as much as the analog)...and the added heat of the additional power needed in analog xmtr...
Add all this up and its a LOT of cash
2) Use same FM analog xmtr and add digital xmtr with separate feedline to antenna that can take both signals through different ports...FM analog stays the same, digital xmtr is lower power but new antenna needed (or retrofitted) and additional feedline for digital signal
3) Space combining using licensed analog aux antenna on same or close by tower...analog is no different than it is now...digital is running 1% of analog...both antennas must be non directional and have similar patterns...this works IF the aux antenna meets certain criteria..otherwise, no go..
4) For MASTER antennas only like Sr Road, #2 is used but the hybrid combiner is used in reverse...and to describe it would take MUCH more detail than I can do here...but the combiner at Sr Road was a Reject combiner and not a pass combiner as is needed for this method...thus they will be changing the combiner out to a new Pass only combiner....which is a little larger but works MUCH better...and using the reject port as the digital input which then is isolated from the analog high power input...the digital signal travels in the opposite direction through the combiner and comes out on the far end of the system...
then it goes through a separate splitter and up its own feedline(s) to the antenna where it feeds a different port on each bay...thus being isolated but getting the same antenna array...(the analog is right hand circular and the digital becomes left hand cirular polarized signals!)...
Whew...my hands are tired!!!
Hope that helps a little...if I can get an image scanned in and figure out how to paste it here, I will try to do that over the weekend...it shows the ideas much better in detail...
> they half to put up another antenna? or can they broadcast
> it onto the same antenna?
They could if the antenna could take the extra power and/or the digital input....Digital stations are at 1% of the analog TPO (Transmitter power out) so for the 9 stations there, adding digital in one method which I think they will use will require new combiners and a second feed to the antenna....the antenna (a Harris/now Dielectric Cavity Back Resonator or CBR panel) does not have the second port for the digital feed as it was installed and modified from the 1980s till present. Thus a new antenna will have to be installed or at least new input ports along with a second feedline to the digital inputs (which will be left hand circular polarized).
There are several ways to do IBOC on FM...One way is low level combining where the two exciters (at low power) are combined and then amplified by a common linear amplifier...and then on to one antenna...BUT the amplifier in current FM analog transmitters are Class C Mode (not to be confused to a Class C FM station). A class C amp is non linear and is only good for FM and other non AM signals. Thus all new xmtrs must be installed...a lot of cash!
The other methods are high level combining.
1) Use same FM analog xmtr and add digital xmtr using coupler...analog xmtr must run higher power than it does now....if not, time for a new FM analog xmtr...more money....also coupler DUMPS the added power (due to the coupling) into a dummy load....HEAT is wasted RF and dummy load is needed..more money..
digital xmtr must be running 10x needed power...and that extra power is also dumped into the dummy load...thus lots of heat...and increased cooling if dummy load is in same room...plus the heat of the digital xmtr (not as much as the analog)...and the added heat of the additional power needed in analog xmtr...
Add all this up and its a LOT of cash
2) Use same FM analog xmtr and add digital xmtr with separate feedline to antenna that can take both signals through different ports...FM analog stays the same, digital xmtr is lower power but new antenna needed (or retrofitted) and additional feedline for digital signal
3) Space combining using licensed analog aux antenna on same or close by tower...analog is no different than it is now...digital is running 1% of analog...both antennas must be non directional and have similar patterns...this works IF the aux antenna meets certain criteria..otherwise, no go..
4) For MASTER antennas only like Sr Road, #2 is used but the hybrid combiner is used in reverse...and to describe it would take MUCH more detail than I can do here...but the combiner at Sr Road was a Reject combiner and not a pass combiner as is needed for this method...thus they will be changing the combiner out to a new Pass only combiner....which is a little larger but works MUCH better...and using the reject port as the digital input which then is isolated from the analog high power input...the digital signal travels in the opposite direction through the combiner and comes out on the far end of the system...
then it goes through a separate splitter and up its own feedline(s) to the antenna where it feeds a different port on each bay...thus being isolated but getting the same antenna array...(the analog is right hand circular and the digital becomes left hand cirular polarized signals!)...
Whew...my hands are tired!!!
Hope that helps a little...if I can get an image scanned in and figure out how to paste it here, I will try to do that over the weekend...it shows the ideas much better in detail...
- Status