Hi Ralph, > Ralph <w7...@...> wrote: > I have never seen or used a Hamtronics preamp. I don't > know anything about their specs or how truthful they > are. Maybe some one out there in the great bits might > have an answer. Skipp? Eric? anyone??
I'll answer up to the anyone label... Through the years Hamtronics has offered up a number of quite different RF Preamplifier kits and assembled boards. Relative to the industry they are truthful and their products are a good dollar value. Even more valuable is the experience and knowledge many people receive for constructing and setting up their kits. The RF Preamplifier you're probably talking about is not a true helical filter design. Hamtronics no longer offers the HRA series with the on board Toko (brand) helical filter. Their current products (when I last looked) were broad-band and some with modest tuned circuits, which is not really a true helical layout. After completing a recent very large vhf receiver site distribution project... I'm now not so keen on using and depending on or trusting the classic (Toko) type Helical filter assemblies in front receiver pre-amplifiers at locations with strong adjacent signals. The shining star in this most recent project was the now famous GLB pre-amplifier. Please don't confuse my description of the small Toko helical filter assemblies with the helical filters built into many receiver front end circuits/layouts. However, both the performance of your receiver can be and is often directly related to both... but you often can't easily change the receiver (as-built) front end assembly. "You get what you get" built into the receiver as supplied by the manufacturer. After reading your posts and all the answers... I can write is how I personally would want to know more about the Vertex radio receiver front-end layout before I started making changes. Directly dependent on the receiver front- end layout and performance... would say a lot about what you can successfully park in front of it (the receiver). My personal suggestion is that you replace the LMR-400 coax with almost anything else... with relatively short VHF lengths RG-214 mil spec is probably a great choice if you don't have access to free-bee (gratis) hard line. As previously reported many times... I source a lot of repeater problems back to LMR-400 cable so I jerk it out of all our duplex (repeater)operations. The Internet Wifi guys like and swear by it a lot (because of the lower cost) but their operations are mostly half duplex (simplex). Half duplex radio operations don't appear to suffer the LMR-400 type grunge problem nearly as much as the many repeater (full-duplex) gremlins we've had to resolve. But I have seen a fair number of Wifi problems related to using LMR-400 but a lot of that sort of blame gets put off on the path being bad or co-channel interference. It's very smart of you to pay attention to the antenna beam-width related to both your elevation and location of the majority users. A smaller part about how much Transmit Power you use is modestly inter-related to your hardware and how hot you want the receiver side of things. Less TX Power Out is easier to deal with... but I do like a very solid TX signal on/at the user end. There are a gazillion pre-amp and filter options possible... for me it comes full circle back to the receiver performance and how it's laid out (constructed). Commercial mobile two-way radios can be decent repeater receivers and some can be "not so good". cheers, skipp
