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Favorite 50-100W FM Exciter

B

BobOnTheJob

The GM is feeling generous and wants to stock a 50-100W exciter and he gives you a $2500 check and says have at it. What model would you pick?
 
With your budget, I vote for Bext. I have used their exciters and amplifiers for years with good results.
Sometimes they have demo units from trade shows at a significant savings. Talk to the lady sales manager. JBI
 
Bext and Armstrong, I believe, are both RVR. OK as far as they go, but for around 2500 the best you are going to do is 30 watts, unless you catch a clearance special or go P-Tek.

Remember, if you want something as a back-up to a transmitter, rather than just an exciter, you will probably need to add an outboard low pass filter. A number of these low end exciters don't have them, counting on the transmitter's filter to catch out-of-band emissions. Once you get above the 30 watt exciter level, though, it is likely that the filtering is included. Check the spec's.
 
Group in question has a couple of FM2.5H3's with the IPA bypassed so 50W is a minimum. The Bext LEX50 would have been a great match below the price point but of course, it's no longer made, having been replaced with a 150 watt model IIRC.
 
The winner for features vs price has to be Broadcast Warehouse. They are type certified for LPFM and all other services as a stand alone transmitter with no external LP filter needed. Inside the exciter is a version of their DSPX-Mini digital audio processor which will accept analog or AES input and a Web-enabled remote control/monitor. Nobody else (that I know of) comes close to the value, though I also like Bext and Nicom (Nicom is also certified as a standalone transmitter) for lower dollar units and Nautel on the upper tier. I've found all to be pretty reliable. Also worth mentioning is Crown which are also certified as a standalone transmitter and built like tanks.

Finally, although much maligned, I have a 300W P-Tek in service that has been doing continuous duty for several years and continues to just make RF. It's the only one I've ever had, so I cannot speak to the general plus and minuses of the line, just my specific unit.
 
Heard horror stories on some ptek models,the gamma series may be improved.I like the BW and Nicom NT 250 (5 to 300 wattts).Have several on the air on lpfm's,one in service since 2003,service free.Used Bext units which are RVR's,they do a good job as well.But one is my all time favorites is the BE FX50.Great box.
 
Kmagrill said:
The winner for features vs price has to be Broadcast Warehouse.
Click to expand...
I failed to consider Broadcast Warehouse...their 1W exciters are flat down to 1hz and sound awesome. It just never dawned on me that they made a 50W exciter for under $1700. I have some research to do and may well look like a hero thanks in part to BW and Kmagrill. Appreciate the post!
 
call Mike at scms.he may cut you a great deal on the 150 watt version.Then you could just run under half throttle and you'd also have extra power if the main xmtr crashes on you.
 
oldiesstation said:
call Mike at scms.he may cut you a great deal on the 150 watt version.Then you could just run under half throttle and you'd also have extra power if the main xmtr crashes on you.
Click to expand...
Good idea...will do.
 
To be clear, the BW transmitters only recently started incorporating the integrated Webserver remote interface and the DSPX-mini processor (sometime around NAB of this year). You want to to avoid the older units with the embedded analog processor which is not nearly as powerful as the DSPX-mini. There may be some of the older units still in USA stock, so be sure to verify before buying.

You might be able to get the 300W transmitter within your budget. Having the extra power available is nice for emergencies. The BW 150 and 300W models use the exact same final amp. On the 150W model the power supply voltage is lower which limits the output power. The final transistor is a dual MosFET like a BLF278 or SD2932, rated for 300 or 350W, so if you're running 100W or even 200W, you're well under the rated capacity of the final.
 
Wonder why BW's website hasn't been updated with the newer xmtr's? I had a pic of the newer series that was emailed to me.Maybe they had issues with them.Nice looking unit but for the difference in what i was priced i would get the Nautel VS300.The ones on their site are much older models.Scott lurks on the board
sometimes,maybe he will chime in and tell us the latest.cheers..
 
There are some of the new ones in the country. I know of a 1kW unit being installed next week, however, I believe it's a loaner unit until the production ones can be delivered.
 
I had a 2.5H3. Had a pair of used BE FX-50's, the FX-50 worked fine driving the Harris directly.
If you can find a used Continental 802A or FX-50, either should work fine and will be a much better buy than the Broadcast Warehouse toy. I've seen 802A's go for around 1K.

You really only need to have about 25 watts to drive the 2.5H3 to full power. Heck, I could get about 1200 watts with an MX-15 driving it. We were originally licensed at 1,050 watts, then got an increase to 2,450 TPO, when I bought the FX-50's. The IPA in that transmitter was little more than a buffer amp, though consider the original exciter was the 7 watt TE-3.

Make a quarter-wave shorted stub and "T" it into the feed to the final. Isolates the exciter from the final circuit, in the unlikely event of a short.
 
BTW. Broadcast Warehouse does not manufacture FM transmitters, and has not for six years now. The transmitters that are being mentioned are those of BW Broadcast :) :) :)

And yes, the current transmitters have built in 4 band DSPX-MINI processing (factory presets on a dipswitch) and analogue, AES and MPX inputs - in addition to the respected analogue fm exciter that is ultra transparent.

There is an interesting whitepaper that has some nice spectrum analyser plots of the TX150 that is being discussed above and demonstrates how clean it is.

http://www.bwbroadcast.com/news/useful-articles/dds-vs-analogue-exciters

Regards
Scott
 
So I see. To drive a 2.5H3 the 50 watt model would make the most sense--you would still need the shorted 1/4 wave stub to protect it.

One problem with newer exciters is the VSWR protect circuits. Some just fold back, some shut down, some are more finicky then others--e.g. the 802B. Makes it difficult to match into the grid of the final on the Harris box if the exciter just shuts down. If the circuit folds back, you at least have a chance to walk in the grid match to where the exciter is happy.
 
Maybe a 3-port isolator of some sort would help with the vswr shut down?
Use them on Marti RPU's & STLs since they get weird looking directly into cavities.
 
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