70cm amplifier

On Ebay in Germany I found this module, bought it for 64 Euro. After mounting this on a suitable heat sink and adding some connectors to it I started testing with 28 Volts.

Mirage VHF/UHF Amplifiers

Power output and gain were disappointing I could get about Watt with 20 Watt drive with full compression After increasing the supply voltage to 32 Volt power output increased to Watt. When looking at the specifications of the BLFA then it was clear that the amplifier was not working as it could download the Specifications from the BLFA I started measuring the gain of the amplifier at different frequencies Using a signal generator at 10 milliWatt I measured output at different frequencies.

I decided to try and see if I could optimise the amplifier After adding two tuning capacitors at the input I increased gain from 11,7 dB to 18,9 dB so quite a lot difference Power output increased to Watt max.

I tried adding a tuning capacitor on the output and power output increased to Watt with 17 ampere total current, I replaced this with two small SMD capacitors of 5,6 pF on each output of the BLFA so 4 in total. I added on the input of each transistor a trimmer see the picture above. The maximum capacitance of the trimmer is 45 pF I added on the output of each transistor two SMD capacitors, nothing special, of 5,6 pF On the picture below is visible were I did put these, the capacitor on the right is mounted on top of the capacitor which is already on the circuit.

The way I mounted the coax cable: The total amplifier ready for use, the output dummy is mounted on a small alu block to level of the connecting strip to the circuit board. Some lessons from other Hams who made these modifications: Do not remove the housing from the amplifierleave the housing on as it is.

Mirage VHF/UHF Amplifiers

If you remove the housing and do the modification you have big risk that the amplifier starts oscillating. After modification max drive power needed is about 5 W to get Watt output. Use a good reliable power meter to measure output.

I also have a schematic diagram available and some spe4cifications from the amplifier These can be downloaded Schematic diagram Specification. Frequency MHz output power mWatt Gain dB 11,7 12,4 13,5 12,3 10,8 60 7,7 I decided to try and see if I could optimise the amplifier After adding two tuning capacitors at the input I increased gain from 11,7 dB to 18,9 dB so quite a lot difference Power output increased to Watt max.Return to front page. Finally the kits arrived from china and very much in a similar condition to the wideband VHF kits in the last article.

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Once again a pre-used transistor and ATC capacitors but everything else was new and shiny. The above photo is of the components as supplied when I opened the antistatic protection bag. Far too many 10K resistors and spares of most components although the 30pF missing! The decoupling capacitors again unmarked so again I must dig out my trusty Wayne Kerr bridge.

I started in a similar manner to the MHz kit and soldered in all the components associated with the Bias supply which is subtly different in design to the VHF boards.

70cm amplifier

I noticed there is provision for an external bias voltage to be fed directly onto the 50 Ohm current limiting resistor which I must say seems a bit big for the job! I then inspected the contents of the ATC capacitors packed in a separate antistatic bag.

There were 10 in total which confused me as an inspection of the layout given on the vendors website indicated 12 might be required. Editor's note. In one of my kits the 10N capacitors had been replaced with 1N.

They are only used for additional supply decoupling and this appears to have had no effect on circuit performance. The layout photograph on the website shows 12ATC caps and clearly the ones I was missing were the input line caps.

I did happen to have a couple of 30pf ATCs in my junk box and so I used these but at the low drive levels used I suspect any surface mount or maybe even a leaded ceramic capacitor would be fine in this location, maybe even trimmer caps…. Install the remaining components and then cut and trimmed the two pieces of feeder supplied to 10cms as specified. See note below regarding line length. I finished off by winding the coils for the two drain inductors and the coils in the filter section of the board.

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The wire supplied was very stiff and not the easiest to bend. Scrape, or melt the insulation with a hot iron, before soldering. Before fitting the transistor apply DC and check the voltages are correct and the gate bias can be varied smoothly. Return the gate supply to zero after testing. Install the transistor and set the bias voltage using the onboard pot.

The recommended Idq for this transistor is mA per side giving a total bias current of mA. I decided on a slightly lower figure to start with and set my board to mA total bias. It might be judicial to remove the series ohm resistor between the pot and the Zener just to give a bit more headroom on the adjustment. This board has separate feeds for the two Drain supplies so it would be possible to measure each half of the FET if required.

I carefully applied a drive level of about 4watts having first fitted a dummy load onto the output of my Bird power meter and discovered that I had a considerable output power of about 80Watts. The input line specified was for 10cms of the small diameter coax and a quick calculation of the quarter wavelength at MHz using an assumed velocity factor of Replacing the input matching line with a length of 50 ohm PTFE feeder corresponding to a quarter wavelength at MHz namely Presumably therefore the same change might benefit the output matching so I furnished another QRZ Forums.

It's a subjective thing again I'd recommend a second radio, that way you have a spare.

100W UHF Linear Amplifier

Last I looked a single band mobile can be had for less then a amp for an HT, so in the long run that is a much better deal; even if it is replaced with a better rig later; because it gives you a spare, or one for home and vehicle along with the HT for portable use. One can never have too many radios GYQ hit all the points I was going to bring up.

I agree, buy a mobile radio and save the hand held for when you need it and what it was designed to do. You are wise to also consider an antenna.

70cm amplifier

Here is one site for yagi construction data that will work indoors. K7FEMar 6, I also agree. And I hear lots of good reports on the Yaesu K9KJMMar 7, I'll add a new wrinkle to this fabric. This is the only setup I use for mobile operation. I dislike it: the Linears don't have a preamp, and even local signals that I receive are less than full quieting.

I can be full quieting INTO the repeater but have plenty of noise on the output. Same thing happens on both amps by the way. I will be saving my scratch for a decent mobile rig Try to measure it. If it is more than a db, then it is a bad design or defective. Most any commercial tranceiver will have a lower noise figure than preamplifiers built into RF power amps.Your JavaScript appears to be disabled.

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Please upgrade your browser from current version. Learn more about TLS. Simply select one for the band of operation and power level you need! Mirage Amplifiers are compact, instant-on, Solid State, no-tune amplifiers that give your signal that extra punch to get out further and to be heard more clearly.

They deliver the clean and crisp RF power you want. Order one for 6-Meters, 2-Meters Read More. Show Less. Want your order tomorrow, April 10?

70cm 430MHz UHF RX/TX Preamplifier

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Microwave Modules MML 432/100 70cm 100w Amplifier

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Mirage Amplifiers are compact, instant-on, Solid State, no-tune amplifiers that give your signal that extra punch to get out further and to be heard more clearly. They deliver the clean and crisp RF power you want. Order one for 6-Meters, 2-Meters Read More. Show Less.

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Items in Cart 0. Search Within Results. In-Store Pickup Location Close.The gain is adjustable so that the gain distribution can be optimized for coaxial cable loss that can be significant on the 70cm band, and also to suit the receiver gain. An on board bias tee DC power injectorallows the pre-amplifier to be antenna mounted and powered via the coaxial cable.

A Tuned input T type filter and output low pass filter provides high rejection of signals at and over MHz.

BNC connectors are not available on the masthead version. Transceivers without this function will require an external bias tee like the Mini-Kits EME to supply DC power up the coaxial cable. When using a high power RF amplifier up to Watts, additional sequencing will be required to protect the pre-amplifier from damage. Please Note: Built products usually need to be constructed and can take up to 2 weeks to ship depending on work load, but are normally shipped in few days.

No connectors or enclosure are included. Requires Complete construction. For more information see the EME Kit Webpage Please Note: Built products usually need to be constructed and can take up to 2 weeks to ship depending on work load, but are normally shipped in few days. BNC connectors are not available on the masthead versions as they can be unreliable outdoors.

70cm amplifier

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