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Archive for August 3rd, 2008

Product Review – The MFJ-209 Antenna Analyzer

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Review of the MFJ-209 Antenna Analyzer

Introduction

We have been on HF for a long time over here at frrl.net Southern Command. We never saw the need for an Antenna Analyzer. Certainly, no need when they first came out and were very expensive. But now, Antenna Analyzers have reached a sort of maturity, there are many models to choose from, and they have significantly come down in price. So one could ask again, do you really need an Antenna Analyzer?

A (very) basic Antenna Analyzer

The MFJ Model MFJ-209 at $140 is about as basic as you can get. It generates a unmodulated RF signal from 1.7 MHz to 175 MHz continuously in 6 bands. So that means it will cover all the HF bands plus 2m.
Connected to an antenna it will read the SWR continuously from 1:1 to infinity. The SWR scale is marked off in increments of .2 (SWR is a ratio and is dimensionless) from 1:1 to 3:1. SWR of 3 to infinity is just a red band with no scale graduations.

The MFJ-209 has connections for external power (12 volts) and a RCA jack to connect directly to an external frequency counter. The MFJ can also be powered internally by AA cells – alkaline cells recommended. The MFJ-209 is about as basic as you can get – no frills – no bells and whistles.

Maybe you already have an analyzer – but don’t know it?

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Written by frrl

August 3, 2008 at 10:14 pm

History of Reciever Design – 1912 Regeneration and Building the TecTec 1253

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Radio Design 1912 Style – Regeneration

Build the TenTec 1253 9 Band Regenerative Receiver.  Listen to shortwave SSB, CW, and AM the old school way.  Plus learn something about the history of radio and receiver design.

Resources for this post

History of Regeneration: Invention to Patent Litigation by Prof. Sungook Hong
regeneration_hong

Principles of Regeneration
principles_regeneration

Radio Receiver Design – Old School vs New School

The TenTec 1253 is “old school” insofar as the receiver is a “Genny” or regenerative from back in the 1920s. Its a radio technology from when dinosaurs ruled the earth – before superheterodyne. The TenTec 1253 can receive AM, SSB, and CW from 1.8Mhz to 22Mhz in 9 bands and its a hoot to operate.

But the TenTec 1253 is also “new school”. It is new school in the sense that it uses modern components to implement the old school regenerative technique. A true old schooler would use tubes and discrete components to build a Regen.  The 1253 is old school in new school clothes.

The “new school” part of the 1253 will let you see how some new techniques and technologies work. This includes: varactor diode tuning, integrated audio amplifiers, voltage regulation, and IC-based band switching – no more wafer switches. None of this was around in the 1920s. So only the technique of Regeneration is old. The implementation is new.

Tools for the Build

So what do you need to build this kit. You can read lots of articles on kit building and see what they recommend. Here the list of tools we recommend if you build this kit

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Written by frrl

August 3, 2008 at 3:34 pm

Blast from the past – Our Kenwood Hybrid Collection

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Kenwood Hybrid Radios

For the past month of so a series of Kenwood Hybrid radios have shown up here. Most of them are from e-bay.  I have had good luck with e-bay so far.   But before you purchase on e-bay do your due diligence.  Some sellers on e-bay have no clue abut amateur radio equipment, what the really have, if it works or not, or how to test it.  To some sellers, if it “lights up” when they plug it in – it works.  We know that a “working radio” is much more than this.

eBay Nation

Hybrids in general – variations on a theme

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Written by frrl

August 3, 2008 at 1:37 pm

The Age of SuperHeterodyne – Building the Ramsey SR2 Kit

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The Age of SuperHeterodyne

In 1918 Armstrong developed the Superhetrodyne receiver that incorporated the first local oscillator and intermediate frequency modules. The “superhet” as it is sometimes called qualifies a receiver able to function over a range or band of frequencies. The word “heterodyne” means “beating”, a technique producing a beating or heterodyne frequency by mixing two or more signals in a nonlinear device such as a vacuum tube, a transistor, or a diode mixer. The incoming frequency is converted to a fixed intermediate frequency (I.F.) where amplification and filtering are provided.

In addition, in 1922 Armstrong created the super regenerative receiver, a simplified Superheterodyne that improved the gain while simplifying the adjustment of the receiver. The “Regen” as it was called was qualified as a receiver “unsurpassed in comparable simplicity, weak signal reception, inherent noise limiting and AGC action and, freedom from overloading and spurious responses”, nothing less. The “Regen” radios took the most of very few components. However, as parts became easier to obtain, the “superhet” replaced it in all radioactivities.

Time Travelers?

Can we be time travelers? Well, yes and no. We can be kit builders and maybe later, radio experimenters and tinkerers like those Ham Radio folks of the past balancing theory and experiment to refine our knowledge. We can build kits, learn about electronics, and learn about the history of radio all at the same time. What a great deal is that! If any one of the three aspects above can hook you then the others come along for the ride – and if you are not careful, you might learn something.

Limitations of receiver design in the 1900s

So where are we in time? In the early 1900s we had the Regenerative receiver and the Tuned Radio Frequency receiver. Both of these designs had some drawbacks. The problem with the TRF design is that each stage of the radio had to be tuned to the frequency being received. So as you surfed across the band, you had to retune all the radio stages for that frequency. These radios had as many as 6 knobs to tune the stages as you skated across the band.

Finding the magic black box…

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Written by frrl

August 3, 2008 at 6:50 am

Living Life on HF – The Age of Power

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Now that the FCC has dropped the code requirement a few people may find themselves with HF privileges that they otherwise would not have. So maybe they will venture on to HF. HF – “here lives dragons” – written on medieval maps of unexplored territory; what will you find on HF?

Living life on HF you might get the idea that you need more power – a common theme. When finesse and skill fails – when 100 watts is just not enough – you just need to get more power. Or, at least, that is what “they” want you to think. More power – “that’s the ticket”.

More POWER – How to get it

In this day and age if you want more power you can just go out and buy it. You can buy RF Power from a commercial retailer like AES – we suggest that route over eBay.

The basics of what you need.

It’s not that complex.  Here are the basic things that you will need

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Written by frrl

August 3, 2008 at 6:05 am

Review of the LDG PRO-200 Autotuner

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The Revolution and the Evolution

So whats new in the shack? Whats new is an LDG AT-200 Pro Automatic Antenna Tuner. This is a thing of beauty. It makes the “problem” of tuning – not a problem at all. In fact, you don’t even have to think about it. Tuning and matching an antenna to the 50-Ohm impedance of your radio is now all automatic – not even a button push is needed.

So whats the revolution (or evolution)? Well, “tuning” is now done with microprocessors, thousands of memories, plus the usual hardware associated with switching LC circuits. Here’s how these things conspire to make it all automatic.

There is no longer the need to hit the “tune” button on your radio. Radios that use screwdriver type antennas need a RF kick to get them going. The RF kick of about 10 watts is enough to get the RF and SWR sense circuits up and running in a screwdriver to start the tune cycle. The same is true with a traditional radio with a built-in tuner. Hit the tune button and motors start whirling. They whirl trying different values of L and C to try to find a match. When the SWR is low enough, there you go.

If you are living in the middle ages, then you have an outboard tuner and you have to manually adjust combinations of inductance and capacitance with about 10 Watts out to find the match.

What is common in all these cases is that the tune cycle is not transparent and a continuous low power RF signal is required for tuning.

One up on a popular chicken roaster – “Set it, and forget it”

Did you ever hear the phrase “Set it and forget it? LDG has one over on chicken roasters. You don’t even need to set it – just forget it. Here’s the evolution.

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Written by frrl

August 3, 2008 at 5:18 am

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