Skip to main content

8640Jr Bands

 

8640Jr Bands

Filed in homebrew on May.19, 2012

My 8640Jr has 5 total bands, covering 850 Khz – 31 Mhz.

I took some measurements with the Bandspread Control in the Maximum, Minimum and Midpoint of its range.

I started with the VFO output frequencies, as all of the other bands are arrived at by dividing these frequencies down.

With the Bandspread Capacitor set to Maximum, I had a range of 13.6 Mhz to 27.858 Mhz.


Lowest Frequency with Bandspread Cap at Max
 

 
Highest Frequency with Bandspread Cap at Max

 

Next, I set the Bandspread Capacitor at Minimum. It is clear that this affects the high end of the range much more than the low end.

 
Lowest Frequency with Bandspread Cap at Min
 
 
Highest Frequency with Bandspread Cap at Minimum

Finally, I set the Bandspread cap to the approximate center of its range, and made more measurements.

 
Lowest Frequency with Bandspread Cap at Mid

 

 
Highest Frequency with Bandspread Cap at Mid

 

Band 1     850.0000 Khz         1.9604  Mhz
Band 2     1.7008   Mhz         3.9209  Mhz
Band 3     3.4017   Mhz         7.8417  Mhz
Band 4     6.8033   Mhz         15.6835 Mhz
Band 5     13.6066  Mhz         31.3669 Mhz

Comments

Post a Comment

Popular posts from this blog

Yaesu G-450XL Rotator Repair

Image
  Yaesu G-450XL Rotator Repair Filed in Antennas on Dec.30, 2007 In December of 2007, the rope support for the center element of my Cushcraft A3 broke, requiring me to climb the tower and bring the beam down for maintenance.  At the same time, at had been noticing that the rotator control was not indicating correctly, it was very erratic.  So I brought the rotator down for maintenance, as well. The first step was to mark the side of the case, where the top and bottom of the clam shells connected together.  This would allow me to assemble it in the correct alignment when the time came.   Marked Case of Rotator Next, I took the top cover off.  All of the bearings between the clam shells in the depression on the outside were safely stored.   Top Removed A little inspection revealed what the problem was.  The center gear had broken away from the shaft it was pressed onto.  I tried re-pressing it back onto the shaft, but it was too worn out.  I found the phone number for p
Read more

Building the W8NX Short Trap Dipole

Image
  Building the W8NX Short Trap Dipole Filed in Antennas on May.31, 2021 For the past five years, I have been operating the lower bands (30, 40 and 80 meters) with a trap dipole that was modeled after a web article written by John DeGood NU3E. [1] While the antenna performed well, a monsoon storm last summer beat it up enough that the antenna wire broke at the center balun. So I climbed the tower and lowered the remains of the antenna to the ground for repairs. On closer examination, I discovered that the relentless Arizona sun had taken its toll on the traps. The insulation on the exposed ends of the coax had rotted away. They were still working, but would need to be rebuilt and weatherized to insure good operation many years into the future. Since I was going to have to rebuild the antenna, I started thinking about whether this antenna met my current needs and wishes. I had been wanting to get on 160 meters at this QTH for some time, but my small back yard would
Read more

JuncTek Battery Monitor MQTT Controller

Image
 I recently installed some 48 volt Lithium Iron Phosphate battery packs at the Ranch to replace the 9 year old Lead-Acid batteries that had started to fail.   eg4-lifepower4-battery-48v-100ah   These are rack-mount battery packs that are intended for powering computer servers.  They are reported to work very well in an off-grid power system.  The Problem I had a problem to solve before the upgrade, in that the old 48 volt inverter I had been using in our solar power system required a programming interface to change its operating parameters to match the new battery specifications.  Unfortunately, the manufacturer wants over $400 for the required interface to make these changes.  I am unwilling to pay this extortion money for a simple device that should cost less than $100. The communications protocol and interface is proprietary, so it would take a considerable effort to hack the interface. There are two sets of parameters in dealing with the inverter/battery connections: 1. The chargin
Read more