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+--- Thread: Masthead Preamp enclosures (/thread-334.html)
Masthead Preamp enclosures - VK6RK - 17-08-2017
Looking for information where to buy similar preamp enclosures as below:
![[Image: MINI-2_m.gif]](http://www.dolstra.nl/Antenne%20accessoires/Mast%20preamplifiers/MINI-2_m.gif)
![[Image: MVV_144-VOX_m.gif]](http://www.dolstra.nl/Antenne%20accessoires/Mast%20preamplifiers/MVV_144-VOX_m.gif)
RE: Masthead Preamp enclosures - VK4ADC - 17-08-2017
GME/Kingray MHB001 ??
http://www.minikits.com.au/components/hardware/enclosures/plastic-enclosures/ENCL-MHB001
RE: Masthead Preamp enclosures - VK6RK - 17-08-2017
(17-08-2017, 01:34 PM)VK4ADC Wrote: GME/Kingray MHB001 ??
http://www.minikits.com.au/components/hardware/enclosures/plastic-enclosures/ENCL-MHB001
Nope, not what I need.
Must be like the photo's in my first post.
RE: Masthead Preamp enclosures - VK3ALB - 17-08-2017
Hi Rick,
You can get them from Kuhne Electronics. From memory they weren't too expensive considering they're probably the only ones selling that kind of enclosure.
Perhaps there are knock offs available from China?
RE: Masthead Preamp enclosures - VK6RK - 17-08-2017
(17-08-2017, 05:12 PM)VK3ALB Wrote: Hi Rick,
You can get them from Kuhne Electronics. From memory they weren't too expensive considering they're probably the only ones selling that kind of enclosure.
Perhaps there are knock offs available from China?
Thanks Lou. I'll see what price they come back with.
Have been searching but very hard to find any supplier.
I'm not keen on the Kingray enclosure especially when using LMR400 and associated connectors.
RE: Masthead Preamp enclosures - VK3QI - 17-08-2017
Rick,
The best source of such housings is from UKW Berichte.
see:
http://stecker-shop.net/epages/27edac8b-bca1-4619-a0d8-f53e62f2ef2c.sf/de_DE/?ObjectPath=/Shops/27edac8b-bca1-4619-a0d8-f53e62f2ef2c/Categories/Produkte/15/30
You will need to switch Google Translate on.
Most casing are aluminium body and ABS cover - so for best results you also need to purchase some nickel spray to spray the inside of the casing for effective shielding.
Prices quoted include 19% VAT, but now when you subtract 19% but then add on freight and 10% GST, it pretty much comes out at direct Euro to A$ conversion.
For the prices 12 Euro through to 34 Euro for the largest version, they are good value. Hartwig, http://hartwig-rf.de/ a manufacturer of microwave amps and preamps uses them - that's how I got on to them.
Cheers
Peter VK3QI
RE: Masthead Preamp enclosures - VK6RK - 18-08-2017
(17-08-2017, 11:32 PM)VK3QI Wrote: Rick,
The best source of such housings is from UKW Berichte.
see:
http://stecker-shop.net/epages/27edac8b-bca1-4619-a0d8-f53e62f2ef2c.sf/de_DE/?ObjectPath=/Shops/27edac8b-bca1-4619-a0d8-f53e62f2ef2c/Categories/Produkte/15/30
...
Cheers
Peter VK3QI
Thanks Peter.
Now just have to work out the size needed to suit the preamps I have.
RE: Masthead Preamp enclosures - VK3QI - 18-08-2017
Rick,
Bigger is always better - especially if you are hoping to terminate LDF4-50 connectors!
2 connectors plus 1 plug for wired control (I advise never using DC feed up the coax - always use a separate control cable)
Cheers
Peter VK3QI
RE: Masthead Preamp enclosures - VK6RK - 18-08-2017
(18-08-2017, 12:21 PM)VK3QI Wrote: 2 connectors plus 1 plug for wired control (I advise never using DC feed up the coax - always use a separate control cable)
The preamps are to be used with an Icom IC-9100 that has the DC feed. Much easier as I'm replacing the AG-x5 series.
RE: Masthead Preamp enclosures - VK3ALB - 18-08-2017
@ Peter,
Interested to learn why you would never use DC up the coax Peter? Apologies to Rick for hijacking the discussion.
Not telling you how to suck eggs but I'll give you my take on how DC up the coax should work.
Sometimes as in Rick's case we go with what has already been prepared for us. I think DC up the coax works as long as it is configured to "fail to safe".
This means the DC should be available only when the RX is active AND the DC should energize the relays. It follows that the preamp should be wired to the N.O. contacts. A failure of the DC means the relays are de-energized and the preamp is protected as it is out of circuit. As a bonus the antenna is still usable albeit without the preamp.
You could do a similar thing with two coax feeds (TX & RX) should you be be dealing with high power. DC up the RX cable (N.O. contact) and a nice beefy CX-520D relay to handle the power and further protect the front end of the preamp by virtue of grounding the inactive contact.
Of course, there's nothing wrong with using a separate DC supply but I feel the same rules for relay wiring should hold. Failure of the supply should always protect the preamp and if possible allow the antenna to still be used.
Posted in the interest of learning from others experiences.
RE: Masthead Preamp enclosures - VK3QI - 18-08-2017
Lou,
The reason that I don't like DC up the coax is that you can never be sure that the RF is completely isolated from DC under all conditions (such as transient high SWR) , sufficient to affect the proper operation of the DC applied to the preamp, especially if the preamp requires a bias supply to function correctly.
I totally agree that if possible, the switching should be "fail to safe" provided other factors don't impinge on the operation of the relays.
Of course the controversial question of whether you should leave the DC "on" to the preamp on transmit or not, is another factor to consider.
Cheers
Peter
RE: Masthead Preamp enclosures - VK3QI - 18-08-2017
Rick,
I did not see your comment that you were going to run a 9100 and feed just 10watts (or 50 on 70 or 100 on 2 ) watts up the cable.
My comment regarding separate line switching related to where you are running an amplifier. For example in the setup I use for 1296, there is a 400w+ amplifier feeding RF up the cable, driven by a TS2000X.
At lower powers, DC switching is relatively safe, but if you are contemplating more power, then I would advise separate switching.
Cheers
Peter VK3QI
RE: Masthead Preamp enclosures - VK3ALB - 18-08-2017
Hi Peter,
I had not considered DC on the coax during TX but I imagine there could be issues doing that especially at high power. I know for my FD preamps I only apply DC during RX. Leaving them powered during TX seems somehow wrong to me. I have used those preamps with IC275H, IC475H, IC910H and IC9100 (up to 100W) without any ill effects. Of course those radios are sequenced so the relays never hot switch.
Good work finding those masthead enclosures.
RE: Masthead Preamp enclosures - VK5PJ - 22-08-2017
Hello Rick
if you do order some, would be very keen to hear you experiences with getting them shipped as they look to be a good option if I ever rebuild my mast heads.
Peter, vk5pj
RE: Masthead Preamp enclosures - VK6RK - 22-08-2017
(22-08-2017, 04:25 PM)VK5PJ Wrote: Hello RickHi Pete,
if you do order some, would be very keen to hear you experiences with getting them shipped as they look to be a good option if I ever rebuild my mast heads.
Peter, vk5pj
As per call, I've sent you the Kuhne details.
According to their info, they should fit the MiniKits RX/TX preamps quite nicely, being 90x75x40mm internal.