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+--- Thread: 6 Metre "brick" linear amps ...is there such a thing? (/thread-749.html)
6 Metre "brick" linear amps ...is there such a thing? - VK3LU - 07-03-2019
I have been trawling the internet for the above and all I could find were a few US based amps of 600 watts plus.
Are there such things as 50 watt bricks for 6m?
There are plenty of 2m and HF ones but no 6m ones that I could find. Perhaps I am using the wrong wording.
Nev
RE: 6 Metre "brick" linear amps ...is there such a thing? - VK4ADC - 07-03-2019
The ones you want to look for are actually designed for 66-88MHz for "low band" VHF.
Try this one (30W in lieu of 50W) ::
https://www.minikits.com.au/RA30H608M
http://www.mitsubishielectric.com/semiconductors/catalog/pdf/Silicon_RF_Devices_e_201709.pdf
Use any descriptive words in the PDF to search for others.
RE: 6 Metre "brick" linear amps ...is there such a thing? - VK3LU - 07-03-2019
Thanks Doug,
I was looking for a ready made brick if possible.
I don't think my arthritic fingers would work very well on smd components
Nev
RE: 6 Metre "brick" linear amps ...is there such a thing? - VK3QI - 08-03-2019
Nev,
Do a google search on
andrews RM MLA-100
That will get you 80 watts on 6 metres, plus the added advantage of HF bands as well.
Also very little power required to drive it.
Cheers
Peter VK3QI
RE: 6 Metre "brick" linear amps ...is there such a thing? - VK3LU - 08-03-2019
Thanks Peter,
Looks nice, pricey but overkill really for what I want.
I will have to keep looking.
Cheers
Nev
RE: 6 Metre "brick" linear amps ...is there such a thing? - VK3QI - 08-03-2019
Nev,
The cost of a 6 metre brick of the 50 to 100 watt output range is virtually the same as the cost of an HF and 6mx amplifier.
The costs are all associated with power cables, relays, heatsinks, meters etc. etc. The only difference is the few extra switches and toroids/capacitors for the various low pass filters.
The actual chip used is sufficiently wideband to take 1.8 to 52 Mhz.
There used to be a number of manufacturers who made 6 metre only amps of the 50 to 100watt level, when the solid state transistors were not as frequency forgiving.
But now they have disappeared from the market in favour of the high powered FETs which can do 500 watts with minimal drive with no sweat, provided they have good cooling.
In the second hand market you might find a Mirage 1015G which will do 150 watts for 10 watts in or considerably less out for a lower drive, but they tend to be USA only and the cost after exchange rate and shipping is not that much better than what I originally suggested.
Good luck with your hunt.
Cheers
Peter VK3QI
Nev,
I did a bit of a search for a legacy 50 watt 6 metre amp.
Tokyo Hy-Power used to make a couple of 6 metre amps HL-50B and HL-66V.
It just so happens that there is a second hand HL-66V on Ebay USA at the moment.
Price US$ 399 plus $US 120 shipping. That's US$ 519 which equates to about A$740, but you then have to add 10% GST, which Ebay automatically adds. That brings you up over A$ 800.
Nothing is cheap anymore from USA compared with 5 years ago when we had parity with the US dollar and there was no GST to be added!
Cheers
Peter VK3QI
RE: 6 Metre "brick" linear amps ...is there such a thing? - VK3LU - 08-03-2019
Thanks Peter,
The $800+ you quoted is equal to the price of the RM-MLA100 from Andrews!
Yes the days of cheap gear from USA are gone. It's a wonder there are none being made in China like the MX50P which is a reasonably priced HF unit.
I know I'm being a tightwad but I don't see the point of wasting money.
Ah, well. I'll keep looking.
Cheers
Nev
RE: 6 Metre "brick" linear amps ...is there such a thing? - VK4ADC - 08-03-2019
I know you don't want to build the linear but maybe you could talk someone into building it for you.
The centrepiece of any "linear amp" is the amp section itself and there is a kit on eBay that says 3.5 to 30MHz at a price that makes it feasible to contemplate. The kit is listed at https://www.ebay.com.au/itm/DIY-kits-70W-SSB-linear-HF-Power-Amplifier-For-YAESU-FT-817-KX3-C4-003-P8J3/323649910598 and the best part is that it is only about $AUD30 for the basic bit AND is posted from within Australia. There are only a few SMD parts involved with the remainder 'big bits'.
You still need to add the LPF section(s) at the output (it is a very basic wideband amp kit you are buying with this), typically 7-pole, 2 sections, switched if you want it to cover multiple bands. The probability is that it could work on 6 metres too but as there are no device numbers detectable on the 2 x FETs, so you can't tell.
The description is given as:
Circuit class AB linear amplifier for SSB AM CW FM power amplifier for low-power radio power connection；
Suitable for FT-817 KX3 other small power stations
Power supply voltage: 13.8V；Current: 6-10A；Maximum input power: 5W；Maximum output power: 70W
Cooled: fan forced cooling；Frequency range 3.5--30Mhz (10M - 80M)
WARNING: Output prohibit open, short, prohibit VSWR of 2.0 or more
Color: As shown
Material:metal + PC
Package Contents:
1*70W SSB
How good / feasible it is to run at 50 MHz - don't know.
The pricing makes it worthwhile experimenting.
RE: 6 Metre "brick" linear amps ...is there such a thing? - VK5TM - 08-03-2019
They are IRF510 based amps, won't go anywhere near 6m (nor will they do anything like 70w for more than a few nanoseconds).
Also available for a lot less than $30 if you don't mind waiting on the shipping.
RE: 6 Metre "brick" linear amps ...is there such a thing? - VK4ADC - 09-03-2019
I guess that's a fail on that idea/option.
There is still a possibility that the PCB plus most bits could be used with actual TO-220-style RF power FETs that work at 50MHz. It could still be worthwhile experimenting with the PCB using a pair of RD16HHF1 devices to get 35-40 watts out for 1 watt of drive. The S-parameters of the RD16HHF1 (marketed as a HF device) aren't much different at 50MHz versus 30MHz.
I know it still falls short of the 50-70 watt target... but it's only < 3dB.
RE: 6 Metre "brick" linear amps ...is there such a thing? - VK5TM - 09-03-2019
That's a possibility, just remember that the RD series pinouts are different from those on that pcb and the tabs are connected to the source pin.