Cobra 350 XL Amplifier Review
“10 meter” or CB amplifiers these days are widely available and it seems that even more older models are now popping up everywhere from craigslist to eBay. While they are illegal to use on CB frequencies I would suspect that there are a higher ratio of amplifiers to operators than ever before.
When you start looking at the different brands of small solid state amplifiers you’ll find many that look very similar such as Palomar, Superstar, Galaxy, and Cobra amps. While they may look similar the quality from amp to amp can vary greatly. You’ll often hear these amps being called bleed or splatter boxes because of the harmonics they produce. For SSB operation many of these amps will leave your signal sounding distorted.
The Cobra 350XL is one of those amps that was produced under a couple of different brand names and while I can’t vouch for the other versions, I can say that the Cobra 350XL bucks the trend of dirty sounding amplifiers.
The Cobra 350XL is a 2 x 2879 transistor amplifier capable of around 260-280 watts PEP output. It incorporates a pre-amp, low/med/hi power settings, and a SSB delay. The case is fairly standard with heat dissipating fins running the length of the top of the amplifier and a plastic cover underneath can be popped out to give you access to the amplifiers inner workings.
The Cobra 350 XL amplifiers use a similar circuit as the Messenger 350HD amps and are labeled as AB class amplifiers. If you read up on your amplifier theory you’ll find that AB amplifiers have less distortion than class C amplifiers but are also less efficient. The result in this case is that the 350XL will draw more amperage to put out the same amount of power as a similarly built class C amplifier but it will have less distortion making it an excellent amplifier for use on SSB. I’ll also mention that the Messenger amps were known for being good SSB amplifiers as well.
With a 1.5 watt deadkey on AM you’ll see roughly 50 watts deadkey out of the amplifier, swing to 25 watts results in PEP output of around 250 watts.
When we look inside the Cobra 350 XL you’ll see pill style transistors mounted on a high quality F4 type board.
For this type of amplifier a deadkey of 2 watts input or a amplifier deadkey of 70 watts with swing to maximum output will give the roughly 1:4 ratio that most people prefer when running amplifiers.
Hookup should be done with at least 10 AWG wire or even larger for best results.
We tested this amplifier locally and during skip conditions and reports were excellent. The overall consensus was that it is a very clean sounding amplifier with little to no distortion. Output is actually quite impressive but it definitely will draw some amps to reach its full potential.
These amplifiers will warm up during heavy use but in most cases I didn’t find that they get is hot as Palomar, Boomer, or other amplifiers with similar fin type heat sink systems. Most of the time I ran the amplifier on the medium output setting with good results and found that it wasn’t necessary to run on high to make contacts.
While the Cobra 350 XL’s are becoming harder to find they still will pop up for sale from time to time on the CB radio forums and on eBay. If you’re a big power AM’er this probably isn’t the amplifier for you, but if you talk mostly on sideband and are looking for an amplifier that will give a nice sound with little distortion the Cobra 350 XL is a solid choice.
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