Wireless microphone frequencies and new digital TV broadcasts

L

LionHo

New member
Been salivating over wireless remotes and was just about ready to order a Nady DKW or 151 VR when I discovered that the new digital TV broadcasts may present a potential interference problem. Seems wireless VHF microphones like the Nady or the Azden have traditionally used a non-utilized portion of the television channel radio spectrum for channels 7-13...but now the new HDTV broadcasts use ALL of the available spectrum.

So since one of the local TV stations has a new digital TV transmitter on Channel 10, I found that I probably will want to stay away from anything between 192-198 mHz on the wireless microphone choices. That would narrow the selection on the Nady DKW (IOW I'd want to avoid what the Nady calls channel N at 197.150 mHz because of channel 10. Even so, if other TV stations pop up, I might be SOL later on.)

Nady technician was able to tell me what frequencies they use, but acted clueless about the digital TV issue.

I'm a couple of hours drive from this TV transmitter but only about 20 miles line of sight... you guys might want to consider this when ordering these VHF units yourselves, or when you're trying to troubleshoot problems with them, etc. Here's a link that helped me find the range of freqs Ch 10 was broadcasting on:

http://www.csgnetwork.com/tvfreqtable.html

The TV broadcast market where I'm at (Monterey County CA) is something like 200th in size for the US. Even this small it's likely other digital TV stations will be popping up soon. Do the Azden units allow the user to select another frequency in the field? From what I can tell the Nady units do not have this feature.

Don't know if Sony still makes them but I've seen a Sony 900 mHz wireless mic unit for about $100 retail but it looks to have even less range than the Nady or the Azden. Anybody tried one? FRS walkie-talkies and other stuff like my wireless internet modem operate in this band, however, so this might be any solution at all.

(Could be worse: turns out the telemetry devices used in hospitals are also on this portion of the pre-digital TV channel spectrum, too. Hospitals can continue to use their existing equipment, but they have to accept interference and can't cause any to the new TV broadcast, which is not exactly what I'd want to hear if I were lying in a bed in ICU with tubes sticking out of me with my life depending on a half a dozen wireless telemetry devices hooked up.)
 
Reading your post made me chuckle. I just imagined I was out with my best rabbit squeal going when the TV station breaks in with war news. How interesting would that be? I feel for your situation but where I live we barely figured out regular TV much less Digital stuff. I'll be fine for a while.

I called just North of Phoenix, AZ 3 weeks ago and didn't have any stray signals with the Nady 151. For $70 I'd buy one even if it was only good for a season just not to have to roll up the speaker wire. Another solution might be to get the commercial calls, maybe they offer different frequencies.

Ed
 
I might have jumped the gun on which freqs would present a problem, but was definitely worth checking out anyway.

I already have a handheld RS Pro 75 scanner for listening to the air-attack and other fire-fighting calls when the Nat'l Forest surrounding me is burning up. So I programmed in what freqs I could (unfortunately can't enter ones in the 200 mHz band on this scanner) to find that even up on my ridgetop Ch "N", the expected bad one at 197.150 mHz, seems okay, but that "B" or 181.150 mHz is terrible. And the bad one's consistent with what a digital signal would sound like, ie there's loud fizz and buzz that don't go away with squelch adjust... but not voices like you'd hear with an analog broadcast.

Did my test on a 5000 ft ridgetop where I've been caretaking an astronomical observatory. No hardwired phone lines and I had to live off an old analog radio link for the first five years. It absolutely drove me nuts with RFI from afar. Even newer cell phones have the problem of seeing too many cell sites at once. I've even had roaming charges on an old analog .3 watt cell phone from a cell site 175 miles away! Routinely pick up VHF TV from 100 miles away, occasionally 150 or 200 mi. Not too many places in the US anymore where this won't apply-- at least from mountains or ridgelines anyhow.

So I'm just looking at this from the perspective of buying new equip and building a new system around, not making do with what I've already got. Wireless mic selection changes the choice of everything else but the input device, from what I gather off the archives. Not wanting to reinvent the wheel here, just looking to work around a fast changing radio spectrum environment.

Looks like I'll probably buy as inexpensive equip as I can (Nady DKW) knowing I won't get but a couple of years out of it tops. By the spec even the cheapo Nady has more dynamic range than the Azden-- yeah, it'll be heavier for the amp and the 12v battery I'll be lugging around. But since my mission is to photo a one of the several mountain lions I'm patterning this spring during blacktail fawning season, fidelity is what I'm after, not weight savings. Already lug 15-30 lbs of gear everytime I go out.

The only thing that remains is to find out whether either the Azden or the Sony has field-selectable freq change feature. That'd be a real plus, might justify spending roughly twice as much.
 
LionHo
I'm not trying to pick at you. I was thinking about Geraldo getting kicked out of Iraq and thinking how funny it would be to have the caller going and an emergency break for the News. I'm sure the frequency's will be jam packed soon. One other option is an Advent wireless speaker. I bought one on E-bay a while back. It is too big for my purpose but you might find them acceptable. There is a mono and stero set that go for under $100. They are 900 mhz as I recall. I sold mine to some other callers and the testing isn't complete yet.

Ed
 
The Azden does have two channels. Can't remember off the top of my head what the specific frequencies are though. It's just an A/B switch on the the units.

- DAA
 
Hi Ed: No offense taken. Just wanted to make the point that with digital TV interference, you won't hear any voices, only static, because the signal is encoded differently than an analog (ie sine wave or microphone/voice) broadcast. Might account for some of the problems others have reported having when their units don't respond to the ferrite beads, etc...

(Iffen you doubts my sense o humor please check out today's post A Rabbit's Dying Wish)

DAA: Thanks, I'll check this out! What model Azden or do you know if they all have the A/B switch?
 
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