Showing posts from July, 2016

Progress on the LDMOS Amplifier

8/10/2016 ~ A Fun Diversion So OK I am easily distracted and once again I am off topic (only this is not political). Shown below is my beloved SWAN120 Single Band SSB Transceiver built in 1962. Yes, this is an appliance and not a homebrew radio. But there is a real story about the company that manufactured this radio and in particular about this specific radio.   In the late 1950's, Collins Radio came out with an amazing product the KWM-1 a 100 watt, SSB transceiver covering the frequency range from 14 to 30 MHz in 200 kHz slices. This was followed by the KWM-2 which essentially covered the then five major ham bands, 80 through 10 Meters in 200 kHz band segments. This was a major departure from the separate receiver and transmitter that ruled the roost from day one. This opened up a whole new opportunity for mobile and portable operation. It was cutting edge technology with a cutting edge price tag! BTW it is rumored that a KWM-1 was used on Gary Powers' U2 spy plane tha

Yikes -- Another Blue Radio!!

It's compulsive ~ another blue radio. Today I painted the front panel of the JABOM radio. Blue is good! I swear the blue color makes it work better. This was another 20 minute job. Pete N6QW

Small Radio --- Big Signal!

A Shirt Pocket SSB Transceiver for 20 Meters! Several years ago I built a shirt pocket sized SSB transceiver --well actually two of them with the second one being  2X2X4 -- yes that is inches. The overall size was actually dictated by the need to have a front panel. If I had used surface mount it could have been smaller still. The transceiver was the subject of an article in QRP Quarterly. This may be one of the smallest SSB transceivers to be homebrewed. Note for the purists I did not say the smallest!   Recently I made a modification to the driver stage which actually was posted on this blog. I now get about two watts out and driving an outboard amp it is good for about 60 watts PEP. Imagine my surprise the other day when ON8KW was calling CQ and I answered him (60 watts) and he came back to me. I got a 5X8 report. Now keep in mind I am using a beam antenna. So once again a good antenna will level the playing field. The LO is a crystal switched two range VXO that covers from

Back to the LDMOS Linear RF Amplifier

7/21 The Role of Analog Pin A8 One action that always has a bit of mystery is how to actually put the amp on line? This amp will be used principally for SSB (voice) but the principles would apply to CW or digital modes. Basically I hear a station or I want other stations to call me and the 1st thing I do is grab the microphone and squeeze the PTT bar. A lot of things have to happen once you key the microphone. Essentially on the amplifier side there has to be a detection that the PTT was closed and then the TR relays are sequenced and the bias applied to the amp. Part of the TR changeover is hardware and another key piece is software. The software essentially runs some tests such as asking are a set of Low Pass Filters in line? Another is the 48 VDC to 12 VDC DC to DC convertor energized? Assuming the requirements are met the important pin is Analog Pin A8. If a low (ground connection) is observed on that pin then the amp is in line. A circuit schematic for A8 is shown below.

Squeezing a few more Watts out of the Cool Blue ZIA Transceiver

Getting More Pout of your Rig! So Ok, we all love to stand on the mountain top and scream I worked a station 12000 miles away on 20M SSB running 100 microwatts. Plausible? Yes! Possible? Yes! Practical on a daily basis? Probably not!   So what do you do to make consistent and reliable contacts? The 1st thing you do is get a decent antenna! A chunk of short wire hiding out in an attic space is not a good start! But a properly designed dipole at 30 feet is much better! Beyond that a beam at 33 feet is even better. So its the antenna for starters.   Next is the rig. You do not need to spend thousands of dollars on an appliance box to have consistent and reliable contacts.  A well designed homebrew transceiver running 5 to 10 watts will result in many contacts. Mating that 5 to 10 watts with an amp can really bore a hole in the ionosphere. I happen to have a really Big Amp -- a 3CPX1500A7 --which will do legal limit with about 45 watts of drive. At 5 to 10 watts it will easily

Simpleceiver Revisited

JH8SST/7's Implementation of the Simpleceiver. For those of you turned off by the LDMOS amplifier project we are making a short detour back to the Simpleceiver project of late 2015 vintage. Jun, JH8SST/7 has built and improved upon the project originally documented on this blog. Kudos to Jun for adding an superb AGC system and by moving around some of the blocks in the project that improve its ability to handle very strong signals. Below is the schematic for Jun's version. Speaking of versions Jun has built both a 40M and 20M version. Linked below are two videos from JH8SST/7 that detail the two versions             Jun also has a blog that shows additional information on his project. Superb craftsmanship is a hallmark of his efforts. Jun's blog is located here.   On my website http://www.n6qw .com is a pdf document that contains the schematic data.     73's Pete N6QW