Re: Henry, TE, TPL, Vocom, Cresend, Milcom RF Amplifiers I have "Selection D", which is all the above in fairly good quantities. Let's talk about them in the listed above order.
Henry: What I call fairly straight forward minimalist layouts, nothing super exotic. Henry does offer Service and it's fairly easy to actually talk with a warm body. There was a report that some earlier Amateur (Ham) Service Amplifiers didn't include the commercial spec low pass filtering. I've not seen a model with the no/little low pass filtering and I pressed one of the guys at Henry for a response regarding the filter statement. He told me "every current Henry Amplifier has trailing low pass filtering"... so until I see otherwise I'll take him at his word. There doesn't seem to be a lot of difference between the more popular Amateur and Commercial Amplifiers and their pricing seems realistic. It's neat to see the occasional 450 to 500 Watt monster Henry Repeater Amplifier come up on Ebay just to watch the sharks circle and attack. Then see the same amplifier relisted a few months later when the original buyer is unable to tame the beast. Like EVERY BRAND of Amplifier I test/use, some of them easily make rated power, others might not and a few even exceed their stated gain. TE: A true love-hate relationship for most... you have one, it works well and it's a pretty amplifier. Or, you have one with an issue and the matching Service/Communication horror story. I love TE Amplifier products, I hate having trying to reach the owner/operator/a warm body on the phone. I have a fair number of TE Amplifiers in service (I buy them used when I can get them for a decent price) and none have failed yet. I have a few monster 250, 350 watt TE Amateur and Paging RF Amplifiers and they even seem to take the limited abuse I throw at them. A first glance under the hood is really an impressive site. I'd tell more people to buy TE Amplifiers except the one time a good friend takes my word and buys one, his or her amplifier will probably be the non-working train-wreck story I've heard about and of course it would be my fault for suggesting the TE Products... so I don't recommend the brand because of the horrible customer service stories even though I like and use their products all the time. I've talked with the owner of TE at a past IWCE Show and questioned him about these stories and provided feedback. He agreed his participation in the Amateur Market could be better and that he/they are trying to improve their customer service. He also mentioned how the Amateur line was much secondary to their other markets but they will try and improve where needed. TE doesn't have a web site that I've found and you have to call and leave a message to have them get back to you for a Catalog or information. TPL: We used to refer to as "Toilet Paper Line" even back in the 1980's... and it seems they've been cranking RF Amplifiers out forever. I've not really seen any bad examples and heard any major credible TPL horror stories. I like their old stuff, their new stuff and their customer service quite a bit. Even the older TPL Products were fairly well designed for what they are. On Ebay and at flea markets they are often the amplifier deal of the day. I've also seen and have a number of rather odd frequency range and mode TPL Amplifiers. In the Commercial Radio World, I use a fair number of the TPL RXR and LMS Series of RF Amplifiers... Depending on how you look at things they almost seem to be repackaged versions of the same RF decks in different physical layouts with various bells and whistles added. Their newer products are quite a step forward in current designs and production. You can see TPL Amplifiers with the top covers off at the IWCE Show (Las Vegas each year) and they're very pretty to look at. TPL makes good stuff and they're a great dollar value on the used market. ... and TPL will sell you parts and they are not shy about providing circuit diagrams with their products. For those of us long time two-way people... one might theorize how the small TPL mobile amplifiers breed in quiet store rooms like coat hangers are reported to do. There just seems to be a million of them out there. Vocom, Cresend: Do we call them the same Company now? Decent designs, many different models, some of their circuits are straight forward, some are pretty wacky. They'll talk to you on the phone but you normally won't get a service manual or diagram. I was told "the circuits are generic enough that anyone with decent RF Experience should be able to repair the amplifier without a diagram, so we don't provide them". While the above might be true in some cases, even the long time RF Head (in field repair person) would really like to have a diagram to reference during repairs and service. There seem to be a number of different Vocom Amplifier generations or at least I have a fair number of different looking and designed models through the various bands. They make/made a fair number of really monster (relative to land mobile applications) RF Amplifiers and like Henry, we have seen some 350 to 500 watt level repeater amplifiers being offered up on Ebay. One other side bar about the Vocom Amplifier Circuit... some of their engineering uses very well thought out power divide and combiner methods, which I really like quite a bit. If you have an impedance match-fault condition, some of the Vocom layouts seem very able to handle and report a problem. I don't see those same methods used on other amplifiers (maybe with the exception of newer Cresend Products. Milcom: Sold out to another Company and at first attempt you can't find out much about them on the web. But their products were OK and fairly straight forward designs. I have one or two in service and they keep on a'talkin so I leave them alone and get on with life. I doubt you'll find very much in actual circuit diagrams for Milcom Amplifiers but a little tiny bit is around if you really dig around. One thing I like about the brand is... every one I have easily makes rated power output plus. Milcom high gain less than .5 watt drive RF Amplifier designs seem to be fond of using wide-band hybrid modules. Once again every brand of Amplifier I test & use... some make rated power, others same models don't and a few even easily exceed their rated gain. Your results will probably vary... often in every example. cheers, s.
