So, I will be upgrading my broadcast chain from dedicated FM exciters to a software defined radio. Either the USRP B100, BladeRF, or HackRF. (Likely the latter two due to price)
I already have cabling, antenna, etc listed and worked out; now I just need to keep the signal clean. Where is the best place to buy a pre-built lowpass filter? Looking for 7pole or more, and I don't want a kit if possible.
I got a very cheap one from Vast Electronics earlier this year, it needs to be fixed into a hobby box and you need to get SMA to BNC connectors (Hobby box and connectors from Maplin). Total cost $10 + $10p+p and the box & connectors about £8.00 (I was in the UK on a visit) Total somewhere around €28.00 or about £24.00 sterling. www.ebay.com/itm/FM-76-108MHz-low-pass-filter-LPF-/261265316498?pt=LH_DefaultDomain_0&hash=item3cd4a05a92
"Lets see' we're on err 92 FM tonight, and it feels like a nice clean little band so far. No one else is using it. The price is right."
Mark Hunter - Pump Up The Volume.
Howdy Dermot; I finally got my NTSC low power analog VHF Television 30 watt transmitter - question, I assume I will need to use a filter on this thing, just as one an FM transmitter?
If so, Can I use the Ramsey one you linked to - even though its for FM, or will I need a special filter made for TV?
Thanks! - not an EE and though sort of a veteran FMer a few years ago, TV is utterly new to me (and a lot more expensive ;-/. and work ;-/.)
Howdy Dermot; I finally got my NTSC low power analog VHF Television 30 watt transmitter - question, I assume I will need to use a filter on this thing, just as one an FM transmitter?
If so, Can I use the Ramsey one you linked to - even though its for FM, or will I need a special filter made for TV?
Thanks! - not an EE and though sort of a veteran FMer a few years ago, TV is utterly new to me (and a lot more expensive ;-/. and work ;-/.)
If you are using channel 2 through 6 then you could get away with using the same filter you use on an FM broadcast transmitter. Any channel above that will require a specially made filter since they are much higher in frequency. It sure couldn't hurt to filter the output even if it is a TV transmitter. Just like with any other transmitter, calculate the harmonics and make sure they don't fall on important frequencies.
Hi Kage - no, I decided to got with Hi-VHF - mainly because I wasn't sure if the new LCD HDTVs had analog tuners that included channels 2-6 (most still have analog tuners today 5 yrs after NTSC shutdown - maybe because licensed low power NTSC stations can still broadcast until Sept 2015 (hell I pick up one on my B&W TV a few months ago)). In fact I just bought a 1080 22" Insignia (smallest true 1080 I could find - not 720) to use as a PC "monitor" with the "video transmitter PC" I'm building (small ITX box - I'm assuming the buildt-in Intel-on-chip-Haswell (the 50 -buck Celeron version just out) GPU will have enough horsepower to playback standard def DVD video out to LPTV trans), this tiny HDTV has an analog tuner and scans for analog at the same time it scans for digital ATSC stations. The TV I bought my mom - Samsung - couple of moths ago - also has an analog tuner.
This makes me happy - it means anyone with a new TV but using an antenna (which is around 20-percent in my neighborhood - and more and more "cable cutter" are created each day I think) will get my signal.
I was afraid that if I went with a Low VHF transmitter, those same new TVs would not be able to receive my signal - since technically TV channels (for both analog (which remains alive until sep 2015 officially anyway)) now start at channel 7 and end at 50?/39? (used to be 83 long ago, then 69, now ??).
It may be that all the new TV simply slap an NTSC tuner in them and that tuner includes the low band anyway - I just don't know. If they do and I knew, I would have gone with the low VHF due to longer transmission distance (but maybe not due to the larger antenna I'd need - so not sure).
Channel 9 has a nice clear space on both sides of it. not to mention all the station idents I copied for use using that number from the Brisbane Ausie channel via youtube clips.
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ok - so I'll have to figure out a filtering solution then - maybe PCS has something - they got an antenna and some transmitters.
Oh I should have remembered that most of the DTV stations now are UHF. Even the VHF stations went to UHF and used a virtual channel number to keep with their original channel number, like our channel 3 here moved to UHF 50 but use a virtual number of 3.1 now so not to confuse people with the changeover. Since most TV is on UHF now almost all of those "digital" TV antennas are actually glorified bowtie antennas so yes you would want to be on the higher channels.
Yes most nationally VHF analog stations went to UHF - but "here" half of them stayed on their analog channels and simply converted over to digital. one of them simply boosted their power to "make it work" a couple of years later. the Lo-VHF band is now "extinct" - but the Hi-VHF is alive and well over "here".
not sure what you mean about "wanting to be on the higher channels (if you mean Hi-VHF or UHF). the FRB unit is Hi-VHF (per my request - decided against Lo-VHF because was not sure if the cheap analog units in new HDTV's received channals 2-6 or not - and finding that info seemed impossible)due to me getting a little better range with the flea power.
I'm just not sure what type of filter I will need - with a 6-db antenna from PCS I'll be outputting 200 watts (5 mile radius?). need to protect FM and Aircraft I assume (below me bet channel 6 and 7) and I assume also protect the UHF band from 14 to now 52? from any dirty harmonics/spikes from my Hi-VHF signal.
....small setback, apparently a Haswell CPU is not the same socket as an Ivy and an Ivy motherboard will not use a Haswell ;-/. dumb dumb dumb of me to buy those two to only later find this out - socket 1155 is not the current standard ;-/.
ugh ;-/. returning the CPU for an older one after the hassle and the restocking of the 45 buck chip vs buying a Haswell motherboard for 60 and lumping the 35 buck Ivy board.
might just keep the chip and buy the Haswell compatable 60 buck board in say 4-6 months for 40 bucks instead.
It will take me that long to sort and configure all the video files and combine all the thousand or so VOB's into manageable playback directories (named by day/date for simple playlist playback - probably 180 days or so, so 180 nested directories - 18 hrs for each - with "sign on" and "sign off" (nice indian head/ rainbow/ and Airforce Flight (T-38/B-36/F-104 versions) vids to use on youtube for this).
just throwing SMplayer into the startup folder and seting windoz7 to startup without login; and seting a schedule program (windowz might have one built it?) to shut down SMplayer and then the OS a few minutes before the mechanical timer I've have to physically power down and power up should work to automate everything.
I'd use Linix - more stable and of course supporior - but even after 5 yrs of HDMI and sound - STILL NOT WORKING - I've just had it with Linux.
my 1998 installation of Caldara' Openlinux had better device driver support than either Mint-13/14 or 15 or the last OpenSuse 13.1.
Kind of forgot about this thread. I now use a BladeRF (Software defined radio) for transmission which has a lowpass filter in the flowgraph. I braodcast on channel 27 with a PSIP of 4-1. Using my PC's GPU, I encode high-defenition MPEG-2 video and AC-3 audio as per ATSC specs.
All you need is a Linux-based computer with GNURadio, a USB 3.0 capable port or hub; an Software-defined radio transceiver, and some SMA-F adapters. Cost me $500 for the BladeRF and adapters.
If you get an SDR like the Blade, there are plenty of "schematics" for well filtered FM transmitters. I even have one of my own that allows one to broadcast DRM digital signals on the sidebands of the analog FM signal, much like HD Radio.
Though, I still need a (better) amplifier. Any tips on a decent linear amp for the UHF band?
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50?/39? (used to be 83 long ago, then 69, now ??).