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Multiband HF Receivers

Click to enlarge 12BH7A 12V Separate Autodyne Receiver by JA9MAT
Features: * Separate OSC Circuit has a stable regeneration. * 4-Bands Coil covers from 600KHz to 12MHz including 7 and 3.5MHz Ham Bands. * Only 12Vdc required. * Using an IC AF-Amplifier for PC.
http://www.geocities.jp/qrper72/12BH7A_Autodyne_Receiver.html

Click to enlarge 17EW8 regenarative radio by JF1OZL
I will show you that, the old triode can be used by low voltage about 12 volts. Please see the circuits. Regenerative radio in old days can make its activity by 17V-DC.
http://www.intio.or.jp/jf10zl/17ew8.htm

All Valve Receiver by SMØVPO
Some months ago I began work on an all valve (tube) general coverage receiver for the HF bands. The prototype is now finished, but as I rebuild it on a decent chassis I will post any correction. This should only affect the coil.
http://web.telia.com/~u85920178/rx/tube-rx.htm

A Regenerative Receiver for Beginners
A modern version of the classic regenerative receiver is shown in Fig 17.75. This project was designed and built by Charles Kitchin. This kind of receiver is easy (and fun) to build ...
http://www.arrl.org/tis/info/pdf/95hb1768.pdf

A Simple Regen Radio for Beginners by N1TEV
Need a simple, fun project - possibly for a Scout Radio Merit Badge? This project is a great way to introduce kids of any age to electronics and shortwave listening.
http://www.arrl.org/tis/info/pdf/0009061.pdf

A Three-Transistor Receiver by W1YDS
Even in this age of crowded bands and sphisticated communications systems, there is room for the lowly regenerative receiver. The unit shown in Figs. 1 through 6 is a simple that should be easy for most anyone to build.
http://www.arrl.org/tis/info/pdf/6803024.pdf

Click to enlarge Battery Powered Tube Regenerative Receiver by K5BCQ
This is my attempt to come up with an improved design point relative to the earlier Air Champ AC-100 and see what can really be done with a Regen.
http://www.qsl.net/k5bcq/REGEN2/regen2.html

Cigar Box Receiver by SMØVPO
I recently sent to QRP@WW a copy of the "CIGAR BOX TRANSMITTER" which was published in the March issue of Practical Wireless. Here is the counterpart to that article, the CIGAR BOX RECEIVER.
http://web.telia.com/~u85920178/rx/cigarrx.htm

CW Receiver for 80 and 40 Meters by KC6WDK
This amazingly sensitive and dependable "Simplest Ham Receiver" is capable of receiving CW (Morse Code) signals. It is crystal controlled and thus very stable and immune to drift and hand-capacitance detuning.
http://cs.okanagan.bc.ca/ve7ouc/eng/kc6wdk-mirror/receiver.html

DRM Demonstration Receiver by DF9CY
In many ways television and radio will change throughout the near future. Especially we will see the change from analogue to digital technologies like DAB and DVB. ... The new technology is called DRM = Digital Radio Mondiale.
http://www.df9cy.de/tech-mat/drm-project/drm-receiver.html

Click to enlarge Fireball SOP Receiver by N2CX
A "universal" CW receiver for 80m + 40m (easy to adapt for other bands). Full featured, yet simple construction and easy alignment. Direct conversion design for simplicity and performance.
http://www.njqrp.org/sop/index.html

Click to enlarge Homebrew General Coverage Receiver Project by Gary Pershin
This web site gives detailed plans of my homebrew receiver. Frequency coverage is from below 300kHz to 30MHz. With this radio you can receive AM, SSB, and CW. Tuning is accomplished with a digital PLL synthesizer.
http://members.aol.com/gapershi/radio/radio.htm

Junk Box DC Receiver by 4S7NR
This idea of converting a super-heterodyne radio to a DC receiver came to me when I was a SWL. I built this receiver from a Junked cassette radio. For long time I used to listen to our Ham friends on 40m using my Junk Receiver.
http://www.qsl.net/qrp/rx/simdc.htm

Click to enlarge Low Voltage Two Tube Regen Receiver Using "Space Charge" Technology by K5BCQ
This was a fun project and all started when I was looking for low voltage designs for a Regen Receiver and matching Transmitter. Several of the guys on the Glowbugs (GB) Reflector reminded me of "Space Charge" tubes ...
http://www.qsl.net/k5bcq/REGEN2/regen3.html

Click to enlarge My First (Homemade) Shortwave Receiver 10kHz-30MHz by PA2OHH
When I made a new start with my old radio hobby, the first item to solve was how to construct something in such a way that the prototype is also useable as the final version.
http://home.hetnet.nl/~pa2ohh/97rx.htm

Regenerative Short Wave Radio by 7N3WVM
If you happen to have a ferrite bar antenna for short wave reception, try to build a regenerative short wave radio like one shown above.
http://www.qsl.net/7n3wvm/regen.html

Click to enlarge Shortwave Receiver 10kHz-30MHz by PA2OHH
This receiver was made with use of the experiences of my first receiver. This new one has some improvements and modifications.
http://home.hetnet.nl/~pa2ohh/02rx.htm

Click to enlarge PLL wideband receiver by JF1OZL
This is a radio receiver covering the frequency from 500kHz to 9MHz. PLL digital tuner is used in this radio, Therefore the receiving frequency is set by the switches on the front panel.
http://www.intio.or.jp/jf10zl/pllr.htm

Click to enlarge Portable Regenerative Receiver With Very Low Supply Current by PA2OHH
It is a modern portable version of the historical regenerative receiver, with transistors and a short telescopic antenna plus RF preamplifier. And it is a real QRP receiver, supply is only 2 mA at 6 volt.
http://home.hetnet.nl/~pa2ohh/02reg.htm

Click to enlarge Small Portable Regenerative Receiver by PA2OHH
The Big portable regenerative receiver is quite successful. The electronic circuit would be very suitable for a small portable receiver if there were not so many controls and switches.
http://home.hetnet.nl/~pa2ohh/03rega.htm

Quick Receiver by SMØVPO
How many of you have got loads of test equipment in the shack that is not really doing anything most of the time. I have got a couple of RF signal generators and a stereo amplifier (for music) amongst other things.
http://web.telia.com/~u85920178/rx/quickrx.htm

Regenerative receiver with 6SN7GT by SM5GNN
This is my October regenny as it looks right now. It works but more adjustements must be done before I'm happy with it. It's based on the 1950 ARRL handbook design.
http://www.algonet.se/~janax/myregen.htm

Click to enlarge Short wave radio by JF1OZL
I will show you one of my first projects. I made it about 13 years ago. This is a radio. It does not have RF amplifier. It has two stage of IF amplifier. It is a normal single super radio.
http://www.intio.or.jp/jf10zl/swlradio.htm

Click to enlarge Simple Regen Radio for Beginners by N2APB
I worked closely with a couple of Boy Scouts in the neighborhood who showed some interest in my "radio stuff", and we together constructed the Regen Shortwave Receiver using Manhattan-style ugly construction techniques.
http://www.njqrp.org/regen/index.html

Click to enlarge Short Wave receiver by PA2RF
The receiver presented here is meant to make a variety of shortwave signals audible. In the first place designed for reception of strong broadcast signals; reception of weaker CW and SSB is possible after adding a simple BFO.
http://www.home.zonnet.nl/laar60/e8.htm

Click to enlarge Softrock: Ein Einstieg in die Technolgie des 'Software Defined Radio' durch DJ9CS
Im Kreis der 'Flex Radio Friends' enstand das Projekt SoftRock, um mit einem preiswerten Empfängerbausatz neue Freunde und Nutzer für den SDR-1000 von FlexRadio Systems zu gewinnen.
http://dj9cs.raisdorf.net/SDR-SoftRock.html

Click to enlarge Softrock Version 6.1 Software Defined Radio by DF9CY
I wanted to 'play' with a SDR = Software Defined Radio. I listened to a talk of OM Bodo Scholz DJ9CS on 1 May 2006 he gave in Eckernförde. It took me some time but in September I ordered a kit for me.
http://www.df9cy.de/tech-mat/softrock61/softrock61.html

Synthesised HF Receiver by SMØVPO
This receiver was originally designed for simplicity and low cost, but, like other projects, it grew. My receiver is now synthesized and the performance is quite comparable to many commercial designs.
http://web.telia.com/~u85920178/rx/synth.htm

Click to enlarge The Progressive Receiver by AA3SJ
Original design by W7ZOI and K5IRK. My version of the Progressive Receiver was built following the schematics and text found in the 1982 ARRL Handbook, section 8-37ff. The original article is found in QST November 1981.
http://www.qsl.net/aa3sj/Pages/PR.htm

The Sudden HF Receiver by G3YCC
The Sudden direct conversion receiver was described by Rev George Dobbs, G3RJV in Sprat number 58, back in 1989, and has proved to be a popular little receiver, for which a kit is available from Kanga Products.
http://www.g3ycc.karoo.net/sudden.htm

Click to enlarge Transistor Radio Receiver by GØUPL
I built this simple regenerative short wave radio receiver in 1982 with a lot of help from my Dad. It ran on a 9 volt battery installed in the back of the box, on the right hand side.
http://www.hanssummers.com/radio/transistor/index.htm

Two Regen Receivers by SMØVPO
I still think that the simple receiver is a very important part of a QRP station. In the 30s and 40s regenerative radio receivers were very popular; they are simple to build & give very good results, even for CW and SSB operation.
http://web.telia.com/~u85920178/rx/regen2.htm

Click to enlarge Valve Radio Receiver by GØUPL
This one was a lot of fun. This valve receiver was constructed in 1988 in the traditional way, i.e. an aluminium front panel and chassis. A mains isolating transformer and rectifier was also required, this was built in a separate box ...
http://www.hanssummers.com/radio/valve/index.htm

 

Multiband HF Transceivers

4-band portable CW tranceiver by GØUPL
This project will be a complete station-in-a-box containing: o CW tranceiver for 20/40/80/160m bands. o Frequency counter/clock. o ATU. o Morse key. o Rechargeable NiMH battery pack. o Space for antenna wire.
http://www.hanssummers.com/radio/portable/index.htm

An experimental DSB/CW QRP rig for 20 and 40 meter bands by iK3OIL
The building of an HF phone rig today isn't shurely a simple job, however I'd like to propose an easy-tomake project, suited for portable or emergency use.
http://www.ik3oil.it/_private/QRP%20sperimentale%20in%20DSB_eng.pdf

Click to enlarge Four Band CW Transceiver by PA2OHH
The performance of the 80 meter CW transceiver using the phase method for side band suppression is very good. Construction was easy with all good obtainable standard electronic components ...
http://home.hetnet.nl/~pa2ohh/99trx.htm

Click to enlarge "HappyHolidays TRX" - A four band VXO tuned 1 watt QRP CW transceiver by PA2OHH
A simple, solid rig for outdoor use during Holidays. More is possible with this solid QRP rig than you should expect. Just try it and do not give up soon!
http://home.hetnet.nl/~pa2ohh/fourbnd.htm

Click to enlarge The Wheel is a DSB Transceiver for 80, 40 or 20 Meter by PA3ANG
The transceiver got its name during the Dutch ‘night owls’ net. We all know the expression 're-inventing the wheel'. People thought Fred (PA0MER) was re-invented the wheel. In this case a transceiver using techniques of the past.
http://pa3ang.nl/index.php?page=hetwiel_eng

HF Tranceiver by EI9GQ
This page will describe the construction of a multi band SSB transceiver. Because I do 99% of my operating on my four favourite bands, I decided to build a four band rig with provision for adding a fifth band later.
http://homepage.eircom.net/~ei9gq/rig.html

Click to enlarge HF Transceiver by I6WJB & I6YPK
The transceiver that you can see in the photo is the result of numerous workhours of Pierluigi and myself. It has been built in two specimens. It is running since several years in our stations and has given us big satisfactions.
http://www.qsl.net/i6ypk/HF1_EN.htm

High Performance HF Transceiver by VA3IUL
High Performance HF Transceiver.
http://www.qsl.net/va3iul/High_Performance_HF_Transceiver/high_performance_hf_transceiver.htm
 

Click to enlarge "HIS TRX" for the Barefoot Hiker! by PA2OHH
It is designed for the Barefoot Hiker. His life style is Back to the Basics and that is indeed what Barefoot hiking in nature and working with the HIS transceiver are. HIS is the abbreviation for He Is Simple!
http://home.hetnet.nl/~pa2ohh/2bnd.htm

The MultiPIG Web Site by W8DIZ
The multiPIG is an Electronic Instrument that functions as an all band QRP Transceiver, a Signal Generator and a Frequency Counter. It is a hybrid between the miniPIG-10 and a wide range PLL Oscillator that I designed, ...
http://diz.faithweb.com/multipig/index.htm

Click to enlarge "MY TRX" All band CW transceiver 5 watt QRP by PA2OHH
"MY TRX" is indeed my transceiver. It is not a perfect transceiver, but good enough for a lot of perfect QSO's. The transceiver has general coverage reception from 1.8 to 30 MHz.
http://home.hetnet.nl/~pa2ohh/01trx.htm

Click to enlarge A QRP SSB Transceiver by WB9IPA
After having been substantially inactive for the last several years, I decided to get back into amateur radio. Having always preferred tinkering with radios over operating them, I decided ... to build a radio ...
http://www.qsl.net/wb9ipa/Gen1.htm

The NorCal Sierra: An 80-15 M CW Transceiver
Most home-built QRP transceivers cover a single band, for good reason: complexity of the circuit and physical layout can increase dramatically when two or more bands are covered.
http://www.arrl.org/tis/info/pdf/96hb1789.pdf

Click to enlarge Wall Wart Powered "Joneset" Transceiver by K5BCQ
My criteria was: - Basic single tube (dual triode) Frank Jones "One Tuber" design point from 1935 for the receiver, but add an RF amp for isolation to prevent uneccessary radiation.
http://www.qsl.net/k5bcq/REGEN2/regen1.html

 

Multiband HF Transmitters

Click to enlarge 5 Watt single-valve transmitter by DL9EBA
I found the description of this small Transmitter in a German Book about German Spy Equipment in WW2.
I was interested in how it works.
http://home.arcor.de/dohmen-hape/ebl21_engl.htm

2 Valve Transmitter by SMØVPO
This transmitter is very stable and will deliver up to seven watts of power with the components and tubes shown. Do not be put-off by valves as they are VERY easy to work with and it seems that there are quite a few valves around.
http://web.telia.com/~u85920178/tx/2tubetx.htm

5-Watt Transmitter by SMØVPO
This is a very simple 5 watt CW TX based upon a TTL logic chip. There is just one "tricky" component and this is Cx. This component should have an impedance of about 10 - 50 ohms at the frequency of interest.
http://web.telia.com/~u85920178/tx/5watttx.htm

500mW CW Transmitter by KC6WDK
A very quick and easy way to get on the air is to build a "Michigan Mighty Mite" CW transmitter for 160, 80, 40 or 30 meters originated by Ed Knoll, W3FQJ and developed by Tom Jurgens, KY8I. It can't get simpler than this!
http://cs.okanagan.bc.ca/ve7ouc/eng/kc6wdk-mirror/transmitter.html

3-Watt, 2-Band CW Transmitter by KC6WDK
More ambitious, versatile, and powerful than the 500mW Transmitter is this enjoyable unit that originally appeared June 1967 in QST. A two-stage crystal-controlled rig for 80- and 40-meter CW operation, it puts out ... 3 watts ...
http://cs.okanagan.bc.ca/ve7ouc/eng/kc6wdk-mirror/transmitter2.html

A Multimode Phasing Exciter for 1 to 500MHz by KK7B
The high-performance direct-conversion receivers described in the references may be easily paired with a CW transmitter to make a simple transceiver of very respectable performance.
http://www.arrl.org/tis/info/pdf/9304027.pdf

An Updated Universal QRP Transmitter by W7ZOI
Looking for a project that will let you try some of your own “scratch built” ideas? Here is a starter low power transmitter circuit for that pursuit.
http://www.arrl.org/tis/info/pdf/0604028.pdf

CigarBox Transmitter by SMØVPO
The text has been copied exactly as it was written when it was published, way back in March 1955 (Practical Wireless). I can clain NO originality for any part of this project. I have built it and it works using DL94 ...
http://web.telia.com/~u85920178/tx/cigartx.htm

Klik voor vergroting Glowbug CW Transmitter by GØUPL
This one-valve (ECL82) CW Transmitter occupies a very special place in my amateur radio history. I was first licensed in 1994 but did not operate on air. I committed to only ever operate equipment which I had made myself.
http://www.hanssummers.com/radio/cwtx/index.htm

Click to enlarge Jersey Fireball 40 by WA2UNN
One of our club elmers, Clark Fishman, WA2UNN came up with a couple of twists on the popular theme of using a TTL crystal oscillator "can" as the heart of a milliwatt-level transmitter.
http://www.njqrp.org/fireball40/index.html

Click to enlarge N7KSB Milliwatt transmitter that's easy to build by KJ5TF
N7KSB's experimental 1/2 watt CW transmitter uses a 74HC240 high-speed CMOS octal buffer, one section which serves as a crystal oscillator, four sections of which amplify this signal, and three sections of which are unused.
http://www.madisoncounty.net/~kj5tf/n7ksb.html

Single Valve Transmitter by SMØVPO
I recently purchased quite a lot of the old "battery valves" at a junk sale. It seems that there are quite a few of these valves around as it is common knowledge that valves are obsolete so no-one wants them.
http://web.telia.com/~u85920178/tx/1tubetx.htm

Click to enlarge The 'Multi-Four' - a VXO Transmitter for 20/30/40/80m by GW4ALG
The transmitter uses a FET VXO; push-pull buffer; 2N2222 pre-driver + BC212 keying transistor; 2N3553 gain- controlled amplifier; 2SC2166 driver and a pair of 2SC2166 transistors in parallel in the power amplifier (PA).
http://www.alg.demon.co.uk/radio/qrp/mf_tx.htm

Click to enlarge The ONER HF Transmitter by GM3OXX
The Oner HF CW transmitter was first described by George, GM3OXX in Sprat number 45 and has been widely used as a simple but effective transmitter. It is so called because it can be built on a PCB just one inch square!
http://www.g3ycc.karoo.net/oner.htm

The 'OXO' All Band Transmitter by GM3OXX
The OXO transmitter was originally described by George Burt GM3OXX in Sprat number 20 way back in 1979 and has proved to be a very popular little transmitter on it's own and as a basis for other rigs.
http://www.g3ycc.karoo.net/oxo.htm

The OXO An all bands VXO Transmitter by GM3OXX
The circuit is quite simple, but the oscillator and the PA are RF and DC coupled; the oscillator will not go without the PA,the 39 ohm and the 0.1uF in the PA emitter to ground.
http://www.qsl.net/g3pto/oxo.html

The VOXNER HF Tx by G4VAM
This clrcult is offered as an exerimental union of the OXO and ONER of GM3OXX fame! L1 has been included to increase VXO shift on 10 metres and higher bands.
http://www.g3ycc.karoo.net/voxner.htm

 

Multiband HF Amplifiers

Click to enlarge Basic Linear Amplifier by SMØVPO
This is both a project AND a bit of basic theory regarding the design of wide-band HF power amplifiers. As usual, it is prompted as a result of e-mail in which I have to repeat myself over and over again.
http://web.telia.com/~u85920178/tx/rf_pa_cct_00.htm

100W HF QRO linear amplifier with Motorola MRF454
100W HF QRO linear amplifier with Motorola MRF454
http://www.cqham.ru/projects/100w_hf_qro/100w_hf_qro.htm
 

1 Kilowatt Linear Amplifier by VK4YE
The amplifier described in this article works satisfactorily with plate voltages ranging from 1.5kV to 2.5kV and easily exceeds 400W pep output from 160m to 10m.
http://www.geocities.com/the_loaded_dog/ham/projects/vk4ye/warning.html

Click to enlarge 4-1000A Project HF Amp by NT8N
This is my new project an 80 -10 meter band switchable HF amp using a 4-1000A. I will be adding to this page as I proceed with the project. So check back often.
http://www.qsl.net/nt8n/project.htm

500 Watt PA by SMØVPO
Although I am an avid proponent of QRP (using reasonable power levels), there are times when I wish that I could run 1,000,000 watts and point it in a particular direction.
http://web.telia.com/~u85920178/tx/500w-txt.htm

Click to enlarge KISS 70W Power Amplifier using VHF Bipolar Transistors by PAØFRI
This 10 - 80 m amplifier is using two VHF bilolar power transistors PHILIPS BLW60. The gain of a VHF bipolar transistor can be very high but the amplifier was perfectly stable in the experimental phase.
http://www.xs4all.nl/~pa0fri/Lineairs/BLW60PA/pa-blw60eng.htm

Click to enlarge A 21-30 MHz low noise amplifier by OZ2OE
This simple little amplifier is using a MMIC MAR-6 form MiniCircuits to give 20 dB gain with about 3 dB noise figure, across 21 - 30 MHz. Selectivity is set by a 21 -30 MHz BPF at the input.
http://hjem.get2net.dk/ole_nykjaer/hfpreamp/hfpreamp.html

A MosFet PA by G3ONL
This circuit was described in Sprat 73 by G3ONL and is capable of 5 watts out on all bands. Diode D1 is included to protect the power device, preferrably a hot carrier or gold bonded germanium diode.
http://www.g3ycc.karoo.net/mospa.htm

HF Bands QRP Linear Amplifier by SMØVPO
This is a rather unusual QRP Power Amplifier design, with a wide frequency response; within three dB's from 300KHz to 30MHz. Overall gain is in the region of 16dB and the final output power may be well over four watts.
http://web.telia.com/~u85920178/tx/linear.htm

HF Linear Amp by EI9GQ
The 50R input of the amp. is matched to the 200R grid resistor by a 1:4 impedance ratio (1:2 Voltage) transformer. Screen grid (G2) voltage is generated by voltage doubling some of the grid drive RF.
http://homepage.eircom.net/~ei9gq/amp.html

Click to enlarge HF Linear RF Power Amplifier by YBØAH
It is nowadays hard to find replacement for RF Final tubes such as 6146B 6JS6 etc. Stocks in the market seem to be very limited, besides it is very expensive too.
http://yb0ah.tripod.com/homebrew/project/pwr_amp/index.html

Masthead PreAmp by SMØVPO
I have received several requests for a masthead preamplifier for use in the VHF spectrum. The power and switching circuitry may be made independant of the frequency so here I have presented two versions of a circuit I used ...
http://web.telia.com/~u85920178/antennas/preamp-0.htm

Click to enlarge Mini power Williamson Amplifier by JF1OZL
When I was about 14 years old, I learned about Williamson amplifier and Ultra Linear amplifier on the radio magazine. Such amplifiers was made by many tubes and Push Pull type transformers. http://www.intio.or.jp/jf10zl/williamson.htm

Click to enlarge My 813 Linear Amplifier Project by WB8ERJ
Actually this rig came back to haunt me. You see when I was in high school, I was a member of an Explorer post that was into Ham Radio. There was a big room full of WWII surplus gear. This particular rig was our "pet" project.
http://www.wb8erj.com/813amplifier.htm

Click to enlarge PL519 FRINEAR 150, 150 W HF Amplifier by PAØFRI
Being a passive-grid amplifier, most of the input power is dissipated in a non inductieve (carbon) resistor applied to the control-grid of the valve. This type of linear has many desirable features, ...
http://www.xs4all.nl/~pa0fri/Lineairs/Frinear150/fri150eng.htm

Click to enlarge PL519 400W Grounded Grid Amplifier, FRINEAR 400 by PAØFRI
The regular visiting of ham flea markets is a money-saving way to obtain parts for a home-brew linear amplifier meeting the requirements of the Telecom authorities.
http://www.xs4all.nl/~pa0fri/Lineairs/Frinear400/frinear400eng.htm

Click to enlarge Push-pull Linear Amplifier with NE592 Driver by DL2YEO
Transformer T1 matches the relatively low impedance present at the VFO FET gate to the balanced inputs of the NE592. With a unipolar power supply, it is necessary to bias both inputs to roughly one-half of Vcc.
http://www.qrp4u.de/docs/en/rf_ampl/index.htm

Click to enlarge QRO GU-84B Tetrode by NI4L
The GU-84B is a ceramic-metal forced-air cooled tetrode intended for use in power amplifiers with distributed amplification and for SSB-signal amplification with output power up to 2.5 kW at frequencies up to 75 MHz ...
http://www.angelfire.com/nb/ni4l/gu84b.html

Click to enlarge QRP HF Linear Amplifier by SMØVPO
This project was a particular surprise for me in that the BC547 (equiv 2N2222) can be used to build a 500mW linear amplifer covering the entire HF band with excelent spectral purity and no neutralising at all.
http://web.telia.com/~u85920178/tx/qrp-hf1.htm

Click to enlarge SMØVPO 500mW Linear Amplifier by VK2 ZAY
This is my implementation of SM0VPO's tiny HF linear amplifier. You can find his original page about the design here: Harry's Homebrew Homepages.
http://www.vk2zay.net/article.php/04

Click to enlarge TB3/750 FRINEAR-750 by PAØFRI
I purchased an old Yaesu FL-1000 (4 × 6KD6) (fig») that had changed bands and countries several times, in the course of which it had undergone various modifications.
http://www.xs4all.nl/~pa0fri/Lineairs/Frinear750/FRI750uk.htm

 

  Update: December 5 2006 © Maarten PG1N