It is exactly as described, in excellent condition, and works perfectly. I have received so many compliments. Paired with my vintage Thorens turntable, it’s an unbeatable match. Great packing, beautiful condition. I’ve been exercising it for the last 6 hours and it sounds excellent! I appreciate the spare lamps for the dial, the test data, the owner’s manual, and your reconditioning effort.

Dual Band VHF/UHF Slim Jim Antenna

The circuit is rather simple, uses only one transistor and few passive components and performs well in terms of frequency stability, almost zero drifting after about 4 hours of continuous operation. With 12 volt DC it will deliver 1 watt RF power. The most important parts of the oscillator are the transistor Q1 and the tuned circuit, which comprises the inductor Ll and the variable capacitor CV1. When the battery is first connected, a brief surge of current flows from the collector to the emitter of Q1, causing an oscillating i.

An oscillating voltage therefore appears at the junction of Ll and CV1. The frequency of the oscillation depends on the values of Ll and CV1, so that varying the value of CV1 tunes the oscillations to the exact frequency required.

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My main shack location has a commercial J-Pole Dual band mounted on a short mast. My workshop under the garage needed to have a separate antenna, preferably hung from a nearby tree. Since I like making things, my first choice was a homebrew antenna. Hanging the antenna from a tree presented several conditions such as a symmetrical design that would hang straight vertically and would preferably not require a ground plane system.

End fed dipoles have a high impedance at the feed point, so some sort of matching is necessary to keep the SWR down. In this case, matching to the feed line impedance is by means of a J-match, just like its cousin the J-Pole. The lower U shaped section below the break point provides the match, in which the feed point is moved to a location of higher current, lower impedance. The feed point location determines the impedance seen by the coax, hence allowing a good match.

These lower portions of the antenna, below the break point do not radiate, since the currents in the two legs are equal and opposite. See the description in the original article by the Slim Jim inventor, F. Judd, listed in the links below.

Magic Anti-Jamming antenna

There is also a wealth of technical information on active loop antennas on his pages. His amplifier kit is an excellent value and has worked out very well for me. I have followed the loop construction guidance on the site. In fact, mine measures at 1.

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FM Transmitters This simple mW transmitter broadcasts audio on With good dipole antenna transmission range up to 4km is possible. Frequency is selected by adjusting R1 potentiometer. Transmitter should be powered by regulated V power supply with at least mA current rating. I must really confess that I also favor this broadcast band, mainly because it is so easy to find signals on the workshop radio. Everyone has an FM radio, and it is fun to play with.

Experimental antennas and the like can all be developed in this band since there are a huge range of “beacons” all transmitting just for my benefit: Basic oscillators also are easy to fault-find in this frequency band, and then later modified for other VHF bands. This made the project easy to duplicate and removed “microphony” the ability of coils to act as a microphone with spring-line reverb.

Session Timed Out

End-fed, half-wave antennas EFHWs are a half-wavelength long and are resonant antennas on the band of interest. Generally, they are not usable on bands for which they are not a half wavelength long. End-fed wire antennas are a different beast. In many cases, the impedance can be transformed with the help of a 9:

This is a valuable need if you have to go beyond the 21 foot cable length that is supplied with a Sirius Indoor-Out door antenna. In order to get the antenna facing in a westerly position, I needed the extra reach afforded me with the fifty foot extension.

Villard, Professor Emeritus of Stanford, founding father of SRI Inc, and one of the most wonderful colleagues with which it has been my sheer pleasure to be associated. Mike had been asked by the Chief of U. His mind set to work: I was at VOA engineering. His proposal became a contract: Mike showed me myriad designs that filled his pool house to the max! We selected two promising ones, and spent the rest of the year studying them, improving them, and producing a really neat end product.

One counters jamming via sky wave, where the jammer propagates by ordinary HF propagation. The other counters ground wave jammers — noise transmitters located near the receiver, usually on the outskirts of the city being jammed.

Stealthy / Covert Antennas

The was the first radio in the series, followed by the S, and finally the SE. He writes “I have located a manual locally VK5 for the AT which by the way, was not available anywhere on the Net, hence my interest in your site I was looking for one. I would imagine a lot of hams would be appreciative for the AT as it is such a workhorse.


FM Transmitters Powerful microtransmitter that can cover 3km range. In our case the output power is about mW depending on the input power of 10mW and 9V battery power supply. The transistor Q1 must be mounted with a heatsink, the heatsink must have small dimensions cylindrical in order not to increase the parasitic capacitance. The trimmer R2 serves to adjust the bias of the transistor, start with the trimmer fully open and close by measuring the current absorbed by the 9V, in my case you get mW at the output with a current of 50mA not increase this value as you only increase the absorption by heating the transistor without increasing output power, because the input power is too low.

Clearly the 9V battery will be able to provide 50mA only for a few hours, if necessary have greater autonomy should be used a larger battery, but it is no longer a bug but simply an FM transmitter. FM Transmitters This tiny Mhz FM transmitter bug measures just 10mm x 17mm in size and as you can see in the photos the biggest components are just the microphone and the battery. You can use a small microphone from an older cell phones, they are small in size and have an excellent sensitivity.

For an effective power supply the 9V battery Duracell is excellent and allows several hours of battery life, but if you want to have a smaller size it is better to use 2 or 3 lithium cells like the used in PCs. The circuit works well from 3 to 12V, the maximum range is obtained with 12V and a piece of cm cable as an antenna. It started with a self-build kit from the Danish manufacturer Jostykit that allowed everyone to build a small FM transmitter for a few Euros.

Such transmitters generally consist of a single transistor oscillator with a simple resonance circuit, sometimes with an extra transistor that is used as audio pre-amplifier. The image shows a few examples that were available in European electronics shops in the mid s.

Welcome to The Crossword Solver

Inverted U antenna for meters An Inverter U for the top band Do you find it hard to get on top band because of the antenna? This is a simple wire antenna that may be just what you need. It installs easily, needs no elaborate ground system, yet performs very well. A small ingenuity solves two connundrums at once — getting the current high in the air, and lowering the current in a very simple ground system.

Common problems — antenna too large One way to meet the size problem is by wrapping a loop antenna around the house, tuned to resonance with a capacitor.

A ¼ wave vertical has approximately a 30 degree angle of radiation, which is an improvement over a dipole, because a dipole wastes so much radiation at higher angles. For short-range communications, a higher angle of radiation is an advantage, which is why dipoles are superior for short-range work.

The first thing you need to know is that ham radio has a loooooooong learning curve. You can be a ham for 50 years and still be learning something new every day if you want to. Also know that Ham radio may not be “plug and play” like you may expect! You will have many questions from the start that are not learned in the “books”.

Get yourself a good local “Elmer” who can guide you on your way! What ham radio equipment do I need? What radio should I get? What kind of antenna? Should I build and antenna or buy one ready made? What bands should I operate on? What are the most popular ham bands for a Technician class operator? How about a power supply, what do I need?

What kind of coax should I buy? What types of connectors do I need for coax?

Inverted U antenna for 160 meters

You may have noticed that almost all my receiver projects on these webpages, up to now, have been based on some variation of a Regenerative Detector, usually a Colpitts derivative. Most QRP designs over the last 30 years, on the other hand, have favored the Direct Conversion approach, which essentially means that we inject our incoming RF signal into one port of a mixer usually a double-balanced diode ring while injecting a tunable VFO into the other port, with the VFO being at just about the same frequency as the signal we want to detect.

So, although we can describe the Direct Conversion circuit as a sort of “superheterodyne” whose local oscillator matches the RF input frequency and therefore has an I. This is not too different from a Regen detector, in self-oscillation, very close to the incoming signal frequency, producing an audible beat note. Another name for a Regen is an Autodyne detector.

Jul 06,  · The Build: I built an experimental antenna similar to the TAK-tenna spiral antenna and was evaluated for SWR response over the frequency range of to MHz, or the meter band.

Any number of situations may call for these measures but the antenna system must still work! Federal law backs up that requirement for licensed Ham radio stations. The power of group pressure. In any event, a brief presentation to the HOA Board resulted in approval. However I keep them very low profile to keep the neighbors happy anyway. Cover, concealment, camouflage — or hidden in plain sight.

I see a quarter wave horizontal mobile antenna for the 20 meter Ham band. Below is a photo of a simple, effective and entirely covert HF antenna.

Building A Multi-Band HF Dipole Antenna