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write your own review of the Atlas 350XL.
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HAMWITHOUTANTENNA
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Rating: 4/5
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Nov 28, 2005 11:52
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Missed chance
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Time owned: more than 12 months
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The Atlas 350XL was packed with lots of clever design details, like an almost inaudible hi-speed T/R switching scheme, one of the best notch filters of all times, an extremely quiet, spurious-free receiver, sideband and CW crystal filters of exceptional quality, an effective noise blanker and a powerful solid state PA.. The VFO was really stable, and the whole rig was built on a sturdy steel chassis that would survive the roughest handling. Quality components and plated-through glass epoxy PC boardswere used. Most circuits had double functions for receive and transmit, keeping the component count low and the reliability high.
But the Atlas 350XL suffered from an enormous number of problems.
Major problem zones, just to name a few, were the receiver AGC and the transmitter ALC, which weren't properly included into the T/R switching, causing loud bumps each time the PTT switch or the CW key was released; RF leakage from the BFO into the IF amp, resulting in a DC offset at the product detector output that changed with AGC level, causing ugly distortion products in the receiver; inadequate gain and frequency response in the transmitter chain, unwanted coupling from the dc power input into the microphone circuits, causing distortion in the transmitter, and an unstable supply for the RIT control. A nuisance was the optional frequency display that wasn't shielded and generated so many spurious signals that it had normally to be turned off.
All of these problems could have been detected and cured within a few weeks of intensive testing. It appears that the rig was developed with a very tight time schedule and released to the market when it was still in a early development stage ( not far from the breadboard stage, to be precise ). What a pity that Atlas missed this great chance.
For a really technically inclined ham, willing to work with this late 70's technology and having profound knowledge in electronics as well as access to professional test equipment and the necessary time, the Atlas 350XL is a rewarding object for restauration, or better yet, for finishing the development work on this basically excellent radio. It has been shown that the Atlas 350XL can be turned into a dream CW machine, where it really plays out its hidden abilities, as well as into a kind of hi-fi SSB rig, with razor-sharp filters in a receiver that is a joy to listen to for hours.
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NC9K
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Rating: 5/5
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Apr 8, 2005 23:09
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Great performing rig set up properly
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Time owned: more than 12 months
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I have been running an Atlas 350-XL since 1985 and only experienced problems when pushing the rig past the limits of the 1980's PA and power supply transistors. I have not experienced the problems described in the post just ahead of this one. I have updated my rig with the following mods and have zero problems under extreme DX abuse. For your information:
The Atlas 350-XL schematic is available from ebay seller wb3cez:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=15050&item=5753912011
The replacement RF output transistors are a matched quad of 2SC2290: http://www.rfparts.com/2sc.html
Eliminate 300pf base-emitter caps on each PA transistor and add 1000pf silver mica directly across secondary of each PA input transformer (some rigs used 1200pf caps on PA input transformer secondaries in place of 300 pf caps on PA transistors - still go to 1000PF). Place PA temp. compensation diodes (there are 2) directly on top of center PA transistors using silicon heatsink compound for good thermal bond. Add 1uf leaded chip cap from PA bias feed to ground on PA board. Add 1uf leaded chip cap across the temperature comp. diode lead to PA board ground where it leaves the PA board. Set keyed PA current to 2 amps with no RF drive. Add negative feedback to each PA transistor base to collector using 1uf leaded chip cap in series with 3 paralleled 120 ohm wirewound resistors. This adds just the right amount of low frequency negative feedback to properly stabilize the PA. Set the ALC trimmer cap. (on back of rig) on 10M with 50 ohm dummy load connected directly to rig. Proper setting will result in ALC limiting output to 100W with front panel ALC control set fully clockwise. 12 o'clock setting will result in ALC coming in at 150 watts out on all bands. Be sure to run proper ALC setting so you don't damage grids of any linear amp connected to rig.
The proper plug and play power supply output transistors are a quad of 2N5686. I purchased 5 for $15- new on ebay. Set supply to 13.5V out.
The power supply power transformer secondary has 3 equal paralleled windings. Split them up and feed them to 3 separate 35 amp 600PIV bridge rectifiers on a small heatsink mounted inside the power supply case. Add a very small low noise muffin fan inside the power supply and position it to draw outside air in through the stock side vent slots and blow air across the rectifiers and the power transformer. Change power supply wires to #6 stranded wire.
These changes will result in the PA outputing 180 watts on 160 and 10M and 300 watts 80 through 20M. You can also add WARC bands to the rig with 3 crystals tied through the factory 10 position aux. band switching. You can figure the crystal specs from the manual. You cannot add 60M.
Many other semiconductors are available from Mouser Electronics.
The receiver is extremely strong per Sherwood Engineering tests: http://www.sherweng.com/table.html
I have been running an Atlas 350-XL since 1985. It is very hard to beat. 73's and good DX Leland NC9K
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KB0PGO
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Rating: 2/5
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Nov 18, 2002 21:06
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Hobby radio
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Time owned: more than 12 months
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I was considered an expert on Atlas radios 10 years ago. I finally refused to work on any more 350XL's around 1994. There were so many problems with them that when they started failing the problems continued to multiply. Most of the problems were due to the weak and corosive nature of the edge connected PC boards and the sockets that will also crack and loosen. There is also a tendency of the PA to go into thermal runaway or self regenerate (becone a power oscillator) and transmit on whatever frequency it wants. It is not a radio that I would recomend to any one except a devoted hobbiest with some substantial electronics knowledge.
The Atlas 210 is a much simpler rig and is actually can be fun to operate. On the other hand, the Swan 100MXA is actually an electronic equivelent of an Atlas 350XL without the mechanical flaws.
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G4VGO
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Rating: 5/5
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Sep 24, 2002 04:59
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A Great Receiver
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Time owned: 0 to 3 months
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I was lucky to find an unmodified 350XL complete with the HEAVY DUTY (35 amp) power supply. It made the trip from the USA in good shape and I was most anxious to try it out. I only operate 160 metres and 99% of that is CW. Bob Sherwood of Drake R4C modification fame gave the Atlas 350XL a good rating in his receiver tests of several years ago and this is the main reason I wanted to try the rig.
Out of the box it performed flawlessly. QSK is as smooth as any Ten Tec I have owned, the power out using the Atlas power supply is 200 watts on 160 metres. The tuning is silky smooth, and the VFO has very little drift from warm-up.
The receiver is a single conversion circuit with a factory installed 500 Hz CW filter. The receiver and the transmitter driver are 'peaked' with a preselector. I live not far from a very high power BBC world service transmitter site on medium wave and the 350XL is the only receiver I have that doesn't exhibit any desense or break through from the BBC. It has a receive antenna input that I use for my beverage antennas and that is something a lot of transceivers don't have.
There are a lot of very big signals on Top Band here in Europe, but the BDR on close-in signals is fantastic on the 350XL. I was hearing weak signals VERY close to EA3JE and his multi-KW 160m CW signal, weak Europeans were readable a few tens of Hz away from other Big Guns. The ultimate filter rejection of the factory stock 500 Hz filter was as good as my Kenwood TS 830S which has a world class receiver also. I was truly amazed! This transceiver's receiver was 95% as good as my R4C with the 600 Hz Sherwood roofing filter, and all of the mods.
Combine this with NO PHASE NOISE and you have a champion receiver. Needless to say I am now a believer. Now to find another one before the supply dries up.
By the way, I did try it on SSB with my D-104 mic and it got very good reports as well.
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K8DIT
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Rating: 4/5
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Jul 21, 2001 04:30
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Worthwhile Bargain
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Time owned: 0 to 3 months
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I was wondering what kind of radio this would be when I spotted one at my friend's house. The vernier tuning knob is it's most noticeable feature. The 350XL is Herb Johnson's last model of Atlas to be manufactured in any numbers, and while it's a basic radio, it works well and is fun to use in light of it's time in history. Some of the devices, like the driver transistor has become extinct. The 350XL puts out up to 200 watts
when used with a 32 amp power supply. I use a 20 amp supply and get nearly 150 watts out on 160, 75, 40 and 20. Less on the higher bands. The reciver is single conversion, but has plenty of sensitivity and selectivity for the ten and fifteen meter bands. It can be used on the WARC bends when crystals are installed and then selected with the switch on the front panel for alternate band use. The digital readout LEDs are also extinct, but found that through emailing some folks, they are available through one of the electronics wholesalers for about $7.50 apiece. I had to replace two of the digits. I took my radio to the one guy who has repaired hundreds of Atlases over the years who happens to live nearby
here in n.w. Washington state. His ad appears in Worldradio and Qst. He found several attempts at repairs that needed to be undone and then repaired correctly. He told me that my finals had been replaced and the good news was that they were done nicely and that they were now better than original, but one of the linkages in the bandpass filtering had been done incorrectly and was probably the reason that this radio fell into my hands so reasonably.
At the end of the repair I had a working radio that is good but not great. The things that work well are the qsk keying and the vox. The reciever is a bit on the noisey side on the lower bands, but the addition of a clear speech dsp noise filter did the trick there. The only other thing was finding a microphone that sounded halfway decent. I found a Turner plus 2 one day and have been getting really good audio reports since. The aux. VFO works fine, the cw and ssb filter are good and I compare it with my Ten Tec Omni D series B Transceiver. There are some things that are better on the Omni and a few on the 350. I found that there are quite a few Atlas afficionados out there still and understand their appeal with use. The tuning knob is unique and actually tunes backwards with respect to the digital readout, but when looking at the analog readout, it all makes sense. So, if you can find an Atlas 350XL reasonably, and figure on spending
from $75 to $300 to restore it to original specs, or if you know what you're doing on your own, you can have one of the classics of Hamdom. It's all solid state, made in the same era as the early Omni series from Ten Tec or the Drake TR 7. The 350 is definitely a step up from the earlier Atlas' series, Mine has nearly no warmup drift. The tuning is pure silk, selectivity and IMD are surprisingly good, and the cw note is crisp and clean.
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