2 meter amp for Flex 6700

  • 1
  • Idea
  • Updated 4 years ago
With FM coming in v1.4,  6700 owners may be looking for a quality amp to utilize their 2M abilities.  DEMI has made one specifically for the 6700 in both 25W and 75W flavors.   I ordered the 75W version with a combined TX/RX antenna connector with fan.  The build time should hopefully put it around v1.4 release for FM fun!

I wanted to put the details here for other 6700 owners to know about.

http://downeastmicrowave.com/PDF/LDPA_PD.PDF

http://downeastmicrowave.com/cat-frame.htm

Many flexers are enjoying DEMI devices.  This will be my first one.
Photo of K6OZY

K6OZY, Elmer

  • 532 Posts
  • 197 Reply Likes

Posted 4 years ago

  • 1
Photo of pa0bie

pa0bie

  • 152 Posts
  • 20 Reply Likes

I am also waiting for FM.  The 75W DEMI is already here.  Working perfect in SSB.

Jan,  pa0bie

Photo of Larry Davis

Larry Davis

  • 69 Posts
  • 12 Reply Likes
do you have the downeast amp just got it  whats your setting for 2 meters
Photo of pa0bie

pa0bie

  • 152 Posts
  • 20 Reply Likes

Yes , the downeast amp.   I have only a XVTR and a PTT cable connection between the 6700 and the Amp.  Settings : Flex pre-amp at 10 db and the output power at 50 %.   That is all.

Succes , jan , pa0bie.

Photo of Norm S

Norm S

  • 64 Posts
  • 3 Reply Likes

I've had the 2N75 LDPA for three months now.  The amp works great with the Flex 6700 but has a couple of interesting things that folks should be aware of.

Once the amp is connected to power, the fan seems to run continuously.   It appears that the thermostat is set for 72 degrees which is a bit too low for my liking.  I contacted Down East and they replied with an email providing directions on how to change the temperature setting for the fan by replacing a resistor.  I just haven't had time to address it yet.

The second issue is that the amp must be turned on in order to receive anything on 2m.   Once the amp is turned off, the receiver goes dead.   This is too bad because I'm sure some folks would like to have a slice sitting on 2m waiting for any possible band openings and not have to have the amp turned on for days or weeks on end.

These two issues aren't deal breakers, but I just thought everyone should know about them prior to purchase so there won't be any surprises.


Norm - W7CK


Photo of K6OZY

K6OZY, Elmer

  • 532 Posts
  • 197 Reply Likes
I just called about mine on order and DEMI informed me that the fan speed ramps so at lower temps its barely audible peaking to 100% at ~100F.   Regardless, the fact that in AZ my house never gets under 80, they put in the notes to design my circuit to start at 85F instead.   Isn't it cool that they will tweak the design for you during buildout?

I also confirmed that the 2M input does go deaf, but he said the unit takes <400mA when idle so leaving it on all the time shouldn't  be an issue.   The fan is also a very high quality ball bearing fan, not a cheap sleeved one.
(Edited)
Photo of pa0bie

pa0bie

  • 152 Posts
  • 20 Reply Likes

My 2M75 is also always powered up as I am in the shack.  The power supply is automatic switch on with the FLEX.  I'am looking for a automatic start for DDutil as soon as SSDR is started.  I need the banddata from DDutil to control the PTT lines to the 2M75 and the other PA's. As long as the TX1,TX2,TX3 and TX-ACC are not assignable to different bands , there is no other way. I have maked a LPT to 16 relays interface boars for it.

Jan , pa0bie. 

Photo of K6OZY

K6OZY, Elmer

  • 532 Posts
  • 197 Reply Likes
Can you explain how you are controlling the TX line to the 2M75 differently than the TX line to an HF amp?  I'm assuming DDUtil would control this.
Photo of pa0bie

pa0bie

  • 152 Posts
  • 20 Reply Likes

Yes , DDUtil can control this.  First I started with the USB-8 relay card , but that didi not recognize the 2m band.  Then I made a 16 relay card , based on the LPT option of DDUtil. Just one CD 4515 ic and 16 times a resistor/transistor/relay. Together with a banddata file in DDUtil , I can make 16 times every band I will. If You are interested then I can send You the file and schematis by E-mail.

Jan , pa0bie.