DDS VFO has been released by KEM

KEM (Kida Engineering Manufacture) has released the DDS VFO kit called KEM-DDS-VFO. It will ship from September 4, but they can accept the order of the kit. It costs 5500 Yen/$47.83 ($1=115Yen). The kit main features are DDS-VFO(frequency set by the botton, offset display, multiply display, sweep osciallation, break-in function, RIT, 30 channel memories, port to rotary encoder) and keyer (auto-keyer, straight key operation, side-tone for keyer and port for break-in).
This kit can be connected to KEM-TX7 and KEM-RX7 for the complete 40m QRP transceiver.
It uses AD9834 IC for the main DDS fucntion, therefore you may check the IC data sheet.

Test is completed: KEM DDS VFO

KEM (Kida Engineering Manufacture) has completed the test of DDS VFO. The picture shows the test board with the 40M frequency. They plan to release it around Sep. 4 because they need to prepare the kit manual.

I'd like to get it for my KEM-TX/RX.

KEM-DDS-VFO

Kida Engineering Manufacture (KEM) plans to release the DDS VFO with the keyer for the next week. The picture is uploaded to BBS. The DDS VFO can be connected to KEM-TX7/RX7 to cover the 40m band, and is also used for a general purpose VFO. The detail information of DDS VFO is here.

I am waiting for the kit for KEM-TX7/RX7 VFO.

p.s. : This product becomes KEM-DDS-VFO-MC50 as of Aug 4, 2009

G3RJV's VXO circuit

The article by G3RJV describes the VXO circuit for various bands. It describes the values of capacitors and inductors on the circuit. It can be a good reference for VXO.

Base Biased tuned VFO

VE7BPO has an interesting article about VFO. It calls the base biased tuned VFO. You can see the 7MHz VFO with three transistors (2N3904s). It covers 6.932MHz to 7.067MHz with 10KOhm variable resister.

DDS VFO for the QRP kits (KEM-RX7 and KEM-TX7)

Kida Engineering Manufacture (KEM) has the BBS for their kits. You may read those message with automated translation from Japanese to English.
The release plan of the DDS VFO is shown with the PCB layout. The new board has DDS-VFO, side-tone, keyer, power supply to KEM-RX7 and KEM-TX7 (why doesn't it have the English page?). I expect that it will be released soon. He mentions the board will be received on Aug. 10 in 2007.

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The DDS VFO kit is available through dx-orders. Here is the detail information of the kit.

PE+SUS (Light-weight antenna wire by Saga Denshi)

The light-weight antenna wire has been found. It is made by Saga Denshi. It weighs only 110g for 22 meters. This page sells at 1380 JPY for 22 meters. It can be used for 40M dipole antenna for 1/2 wave.

When I make my own antenna, I purchase it for HF antennas.

40m CW transmitter by KEM

Kida Engineering Manufacture (KEM) has introduced the 40m CW transmitter kit (KEM-TX7-CW).

The picture is the transmitter board. It is 7.003MHz CW transmitter. You may put your own osicallation input with the external input. It costs 3500Yen for the kit.

The transmitter can work with

KEM-RX7 (40m receiver).

There is no English description, but you can contact KEM about the transmitter kit. Because KEM-RX7 is now shipped to worldwide and they can accept Papay for KEM-RX7 ($36.00+shipping$13.00).

Basic Linear Amplifier

Harry describes the basic linear amplifier for HF transceiver. It is not QRP rig, but might be interesting in the homebrewer of QRP rigs.

The page is well organized and you can understand it easily. Transistors are 2SC2078 with 5-10 watts.

7MHz (40m) SSB/CW Receiver KEM-RX7

Kida Engineering Manufacture (KEM) in Japan has introduced the 40meters (7MHz) receiver called KEM-RX7. It is the super-hetrodyne with 455KHz IF with AM bandwidth. The receiver can cover 7.0-7.2MHz and needs DC5-6V power with 35mA. The cost is here (US$54.87) for DX orders.

Press-n-Peel

Press-n-Peel is a good product to make the circuit board. Its blue sheet can be printed by the laser printer. You can put on the clean copper board with iron. It needs the heat to attach it on the board. It is etched. The board reveals the copper traces with the etching.

NB6M Miniboots

AMQRP describes the miniboots of NB6M with IRF510. The schemantic describes IFR510 (it should be correct with IRF510). This is very simple RF Amplifier for QRP rigs.
This linear amplifier gets 10-14 Watts with 3/4 to 2 Watt drive. The IRF510 is sold by Radio Shack and the number is 276-2072. The specification of IRF510 can be get by the web page. It is Vds=100V, Id=5.6A and Pd=43 Watts.

I've made the miniboots for my qrp rigs and got 5 watts for 1w qrp rigs. You may increase the power with IRF510 D-S voltage. I've checked it with 24V and got 10 watts.

6m 20mW DSP transceiver

I've found the interesting transceiver for 6m DSB. The PCB size is 56mm x 68mm and power is only 20mW. The detail description is written in CQ Ham Radio magazine (October, 2006 issue). It is also sold by the "Calibration" of Osaka, Japan.

PicoKeyer

The QST article about PicoKeyer by N0XAS has bee found. It's very simple key using Microchip 12F629 and 2N7000 for the keying. It is the issue of December in 2003. The keyer software of 12F62o has been stored into the catalogue of qst-binaries.
The software is here.

RF Power Amplifiers

High Frequency Electronics manage had interesting arcticles about PA in 2007. They are Part 1, Part 2, Part 3 and Part 4. Part 2 describes techniques for RF Power Amplification. Class E that I mentioned at the 2N7000 article of this blog is also described here.
Figure 7 of a single-ended PA is a good picture to understand the basics PA.

2N7000 for PA of QRP Rig

A small MOS FET is often used for PA of QRP rigs. Here is the specification of the FET. The maximum Power is 400mW but QRP rigs are used for 1W power output PA. The schemantic of DC40A has 2N7000 for PA and there is no loading resistor. Once the gate of 2N7000 gets the RF voltage, the FET acts as a high-speed switching element. Therefore, the element generates a large power at the switching cycle.

The schemantic shows that the output of Q3 2n3904 is 8V p-p and its of Q2 2N7000 is 45 p-p.

The artcile of MOS FET amplifier is usefule to understand MOS FET. You should understand the properties of FET and how to use FET for the amplifier.

Antennas : Service and Education, W4RNL

L. B. Cebik, W4RNL writes the set of excellent reference articles for antennas. I should read them for my study.

MMR-40

The Hendricks QRP has been announced the rig called MMR-40. It is the good shape of the CW/SSB rig with 6W. The planned shipping is from March 21, 2007.
It is also very reasonable cost ($105 for US, $110 for DX) for CW/SSB rig.

Since there is the PDF doc file in homepage, I'd like to investigate it in detail.

Rockmite power-up

I've check the interesting article about hi-power Rockmite. Here is the article that I've read. You can use 2N7000 for Q6 to get over 1Watt. It's pretty inexpensive to get it.

DC40A is released

Hendricks QRP has introduced the new kit of QRP (DC40A, 30A and 20A). It is the upgraded version of DC40 and more than 1W power with 13.5 Volts. I built the DC40 kit and had a few contacts. The DC40A is also using 74HC4053 for mixer and the front end RF amp is 2n3819. The PA of TX is 2N7000 for more than 1W output. It's the same as DC40, but the output of buffer amp is higher because the resister values of the buffer amp is lower than ones of DC40.
This basic diagram can be also used for 30A and 20A for higher frequencies.

I'm really interesting in the capability of the kit for both RX and TX. I may change TX circuit for old DC40 to get much power than the original DC40 circuit.

The DC40 has the issue on lower audio output and I'd like to know how much it is improved for the DC40A with the RF amp. I may add LM386 audio to get more AF power for the DC40 if it's needed.

Frequency counter with PIC

QRP rig is needed to know the frequency of receiving and sending signals. This frequency counter can be easily built for QRP rig. It uses PIC16F628 and few parts to construct it. The frequency range is 1 to 50MHz with 5 digits.

We may build it for QRP rigs to see the exact frequency of the band.

A POLL ON POLES

W7AQK, David wrote a quite interesting article about the fiber glass pole call Jackite.
Jackite is 31' fibler glass pole can be used for antenna pole. You may check this pole for your antenna support.

2SC1815 mini amp

http://www.geocities.jp/ja3dew/subLinerAmp/C1815CPL4.jpg

QRP-L Mailing list

Here is the archives of QRP-L mailing list. You can find a lot of interesting information about QRP.