I got a second hand R8 which almost looks new. Despite some small assembly problems the antenna shows high SWR on all bands.
By investigating the MN8 matching box it became clear that somebody had a go on it.
The balun looks quite messy and had a broken wire at the joint to the pc board. The balun has an unequal number of turns:
6 turns black wire, 9 turns white wire.
Before I put it up it would be great if someone can help me with the correct data on the balun.
I think you can find the information you require by doing some Googling. There used to be assemby instructions available for downloading of the R5 and R7 antenna's and I think this could have been on the Cushcraft site. I think that MFJ purchased Cushcraft so perhaps a look at their site might be helpful
The balun has an unequal number of turns: 6 turns black wire, 9 turns white wire.
Before I put it up it would be great if someone can help me with the correct data on the balun.
The Matching box for the Cushcraft HALF-WAVE Verticals (R4, R5, R6000, R7, R7000, R8) are virtually all the same (past 25 years),
with some minor changes during that period.
Surplus Polycase EP-8 boxes (black matching box) can be found at Electronic Surplus, Inc. (ESI) in Cleveland. OH.
ESI had 331 in stock for $ 4.95 USD each. SKU: 6007 http://www.electronicsurplus.com/Sea...x?Keyword=ep-8
FAR Circuits (Dundee, IL USA) has replacement PC boards (buy the undrilled verison and drill yourself) http://www.farcircuits.net/
With the web sites below -- you can build a new R5/R7 from raw materials and parts sources.
Check PA0FRI web page for recommendations on insulator repair.
There are TWO approaches (core size and windings) to the 1:4 balun.
This is one area where Cushcraft did change their design (RF power handling) - John, EI7BA and G0WCW cover this on their web pages
The Left photo is the older design (smaller red core with more windings),
the Right photo is the current design (larger core with black/white Teflon wires)
w9gb
Last edited by W9GB; 09-14-2011 at 12:39 AM.
We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths. -- Walt Disney
The R8 is renown to have many problems and isn't their best effort. The R7 was a better antenna.
There's another thread I just saw in the last day or two (possibly on eHam.net) where a new R8 owner found his "brand new" R8 had broken parts inside the matching network assembly.
There's another thread I just saw in the last day or two (possibly on eHam.net)
where a new R8 owner found his "brand new" R8 had broken parts inside the matching network assembly.
I have posted this in the past (with photos of the Amidon cores), but DO NOT PURCHASE AMIDON CORES for the Cushcraft Matching boxes.
Amidon changed suppliers (supposedly to a Chinese company) -- I would imagine MFJ got stuck with some of those cores.
The Amidon cores I had were not sealed and are too soft -- like #2 pencil lead -- I returned in Amidon's original packaging and these cores BROKE in return SHIPPING !
These Chinese "copy" cores break very easily and are NOT suitable for usage with this antenna.
I have found it difficult to get the proper cores in SMALL QTY; Reasonable Prices (~ $10 each or greater); and Good Quality.
I deal with Bob at Balun Designs or other suppliers that produce quality ferrite cores for Cushcraft matching box repairs !!
w9gb
Last edited by W9GB; 09-14-2011 at 12:42 AM.
We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths. -- Walt Disney
Rosevale, Drummanduff, New Inn, Ballyjamesduff, Co.Cavan, Ireland.
Posts
831
There certainly has been a lot of Quality control problems with Cushcraft antennas since MFJ took over, that's for sure!
Fred EI4GMB
'You can never plan the future by the past.'
'Those who don't know history are destined to repeat it.'
'But what is liberty without wisdom, and without virtue? It is the greatest of all possible evils; for it is folly, vice, and madness without tuition or restraint.'
Edmund Burke (1729-1797) Irish statesman, author, orator, political theorist and philosopher.
There certainly has been a lot of Quality control problems with Cushcraft antennas since MFJ took over, that's for sure!
Fred EI4GMB
Sadly, you're probably right. I hate to see that, as Cushcraft had several very solid designs that worked fine for many years. Les Cushman W1BX was a very good "antenna man," and I had the pleasure of meeting him several times in the 1970s when I visited their factory in southern New Hampshire. All that is lost, now.
many thanks for your detailled help. I did not know that the matching networks for those verticals are pretty much alike.
In the past 30 years or so I had the R5, R7 and R7000 but never ever needed to open a matching box !
In addition I had the A3S, A3WS and the early X9. I guess all thoes antenna's are still in use by some other hams.
Since 10 years I built my antenna's myself. They are all yagi types, monoband and are 100% from alloy !!!!
The only exception is the great 2D-30 from CAL-AV, Tucson, Az.
Best 73's
Hal, EA5GNI
One this you need to follow, and that's the recommendation to mount it free, and clear. If it is anywhere near other objects (trees, structures, or the ground), you'll have a bear of a time getting it tuned. If you do get it tuned, if you QSY to a point the SWR exceeds about 3:1, don't use a tuner to get it back flat. Doing so is a sure way to distort the ferrite. I've been there, and done that.
Cushcraft R8 matching network
Originally Posted by EI4GMB
