28 July 2015

Flight of the Bumblebees 2015. N4HAY. Jordan Lake NC

I really enjoyed the FOBB this year. Unlike last year the bands were in good shape and the wx was beautifully mild. I set up in roughly the same spot as last year only this time I deployed a far superior antenna system. My operation did not involve a major trek since I merely walked from the car park to a nearby picnic table. Oh well perhaps next year I will commit to more of an adventure hi.

The FOBB was held on Sunday afternoon from 1pm - 5pm Eastern time zone. Check out the following link for The Adventure Radio Society Flight of the Bumblebees details of the contest rules.

I set up at the Ebeneezer State Park at Jordan Lake North Carolina. This is about a 20minute drive from my QTH. I arrived on site at noon. First I had to build a 40m dipole. I was not well prepared for this contest! I then deployed my 20m and 40m dipoles. This turned out to be more of a challenge than I had judged. Thus I was only QRV an hour into the contest. However once my antennas were deployed they were very effective. My 40m dipole was beaming N-S and was up about 55 ft agl. My 20m dipole was beaming W-E and was up about 45ft. I used my trusty slingshot to launch the antennas to this height.

Rig was a K2 running on the internal battery. I ran a frequency and S&P about 50/50. Battery indicated voltage on the K2 was down to 11volts by the end of the contest.

Band conditions were good and I was able to work almost all stations that I heard. I had the feeling that I could have done better with a W-E facing 40m dipole. Lesson learnt here was to stick to a simple inverted-vee doublet center-fed with ladder line next time. Ideally deployed in such a way that I could change the orientation easily. I am sure I could have done better if I had been better prepared.

I also had problems with my pen that would not write properly! This brings to mind the reason why early astronauts used pencils on their early missions hi!

I was unable to copy my fellow Knights from the Knightlites QRP club Sirs Derek W4FI, JP AB4PP and Paul AA4XX indicating that the 40m band was long.

I look forward to next year's adventure with much anticipation. Many thanks to all stations who worked N4HAY. 72 de Dick.

Log of N4HAY. FOBB 2015. Jordan Lake

N4HAY. FOBB 2015. Suffering no pain!

24 July 2015

Headset Technical Specification comparison

I did a little technical comparison, based on online technical specifications, between the shown headsets. I found it interesting. Perhaps not surprising. On a qualitative level I note a 'very big' difference in sensitivity between the David Clarks and my Sennheisers. However I assume that I am driving them with an amplifier (a current audio  amplifier in my Elecraft K2 ham radio) and  may not necessarily be optimized for either.

I also do notice a difference in both low and high range frequencies between my Sennheiser and Earpods on listening tests. But still the Earpods are very very good and have to be some of the best value for money on the planet?

I would say that all 3 headphones would benefit from a Headphone Amplifier. 

Also note that the SPL measurement is made at one frequency only. Generally seems to be 1KHz. So the sensitivity may seriously degrade at the ends of the claimed bandwidth.

It is interesting to note the technical differences between the sets as optimized for different applications.

Given the complexity of comparing headphones due to many parameters way beyond this list I would think that the 'crowd sourcing' method of opinions may be the best way to make a determination as to which headset is best for you.

Headset technical comparison

18 July 2015

Field Day 2015. WQ4RP. The Knightlites

As in all previous years for me, Field Day 2015 with The Knightlites was a total pleasure! A great adventure and an opportunity to learn and appreciate the challenges presented from operating in the great outdoors in less than ideal circumstances. Certainly that was the case this year!

Four intrepid Knights Sirs Derek W4FI, Joe WA4GIR, JP AB4PP and Dick N4HAY operated Field Day as WQ4RP, Class 3A Battery, NC from the Holly Point State Park at Falls Lake North Carolina.

The Great Setup. Pics by Joe WA4GIR

Sir JP and Sir Derek before the action began. Pic by W4CHX Karl

Violent thunderstorms on Friday evening, and Saturday, destroyed a tent and relegated some of the Knights to sleeping in their cars. But the intrepid few remained at the Key...Sending and Receiving in spite of it all! Great adventure, camaraderie and plain good fun was had for sure.

MRE's issued by Sir JP just in case.  Pic by W4CHX Karl
A shelter destroyed by a violent thunderstorm. Pic by JP AB4PP
20m operating position.
20m operation position. Pic by Joe WA4GIR

Sir Derek WF4I pounding the key on 20m on Sunday morning

40M operating position. Pics Joe WA4GIR

Sir JP at the key. 80m, 15m, 10m operating position. Pic by Joe WA4GIR

Mason (or Consul) Jar LED lamp. A South African product
The Knight's Trebuchet built by Sir Gary N3GO.
This weapon gave us at least a 3dB advantage!
Some finer details of the event.



Operating Conditions

Lessons Learned

Inventory Checklist

DUP Sheet

Here find Band analytical information: 

10 meters

15 meters

20 meters

40 meters

80 meters

All Bands

WQ4RP The Knightlites. Field Day 2015 QTH.  Pic by W4CHX Karl

09 January 2015

Homebrew Attenuator Measurements contd

It was interesting to measure the insertion loss and maximum attenuator accuracy over a wider frequency range.

The BIG attenuator has a maximum attenuation of 68dB.
The Copper attenuator has a maximum attenuation of 71dB.

As for the previous measurements I used the HP 8657B as the 'standard' against which to compare.

I also used a 0dBm input level for the 71dB (copper attenuator) and 68dB (Big attenuator) measurements in order to move the measurements comfortably up from the lower end of the Power Meter measuring capability. The Power Meter in fact showed a consistent slope ranging from 20.5mV/dB for 1.6MHz to 19.69 mV/dB at 450 MHz. Quite cool for a homebrew power meter!

Reference the following links:

68dB slope calculation

Insertion Loss Measurements

Maximum Attenuation Measurements

In conclusion both attenuators show significant insertion loss and maximum attenuator errors for the 148MHz, 224MHz and 450MHz measurements.

'BIG' Attenuator

'Copper' Attenuator

Homebrew Attenuator Measurements contd/

Today I characterized another attenuator recently acquired and known as the 'BIG' attenuator on this blog. The performance of this attenuator over the HF frequency band is not as good as the 'copper' attenuator (results shown in the previous blog). The worst case measurement was on one of the 20dB pads at +1.06dB error. Although this unit is solidly constructed, I assume that the fact that it does not have shielded compartments between each attenuator must degrade performance over the frequency range. Perhaps also the switches used are not as good as slide switches for this application.

The shown measurements in fact are optimistic since they do not include insertion loss. I performed separate insertion loss measurements which are shown in the next blog.

As a part of these measurements I also characterized the slope of the Power Meter.

In conclusion, the attenuator certainly is useful for many functions at HF. Also the use of 1/4 Watt resistors will allow use in higher power applications.

The following links

Measured Attenuation

Pi network resistor values and calculations

Slope Calculations

07 January 2015

Homebrew Attenuator Measurements

I recently acquired a homebrew attenuator (called the copper attenuator in this blog). The construction is modeled in line with the QST article of September 1982 titled "A Step Attenuator You Can Build" by Bob Shriner WA0UZO and Paul Pagel N1FB although the named attenuator pad values were different.

On opening up the unit I was mystified by the values used for four of the PADS. The parallel and series values appeared to have been transposed in error. I reworked these values using standard nearest value resistors.

The switches are in excellent condition with no signs of wear. As can be seen from the linked spreadsheets below, I tested the attenuator over the HF frequency range only. A maximum of 0.1dB insertion loss was observed at 28MHz.

The worst case error observed was +0.4dB for the 16dB PAD.

With all PADS switched in to yield a maximum attenuation of 71dB the maximum error was 0.8dB at 10MHz.

Click on the link below for details of the measurements made. To return to this page please use the back button.
Attenuator Measurements

Click on the link below for details of the resistor Pi Network Values. To return to this page please use the back button.
Pi Network Resistor Values, dB(calculated), Return Loss (calculated)

28 December 2014

ears to our world, HumanaLIGHT and the Joule Thief

I was inspired by the recent excellent You Tube video made by W2AEW showing the HumanaLIGHT.

Reference: https://www.youtube.com/watch?v=qfgX93o8HzY

REF: W2AEW  You Tube #187. " A single cell LED light supporting EARS TO OUR WORLD"

Since the money for this kit goes to a noble cause, I decided to buy one. Check out www.etow.org for more information. In the process I also learnt something about the relaxation oscillator and the idea of the Joule Thief. A fascinating journey for me.

Since all is said on the video I thought I would simply record the results of my measurements here on the blog.

First I tried a dead battery that had a voltage of 0.47 volts open circuit. This did not light the LED.

Attaching a variable voltage power supply to the circuit I found that the LED just turns on at 0.8 volts and 'well on' at 1.02 volts.  Full on was measured as 1.74 volts.

Rail voltage was 1.3 VDC for the first three measurements below.

The circuit oscillates at 10kHz. Symmetrical wave form once fully on.

Here below are some views of the scope waveforms.

Output wave form to the LED. 3 volts p-p. Vcc was 1.3 v dc.
Base of final transistor that is connected to the LED. 

Capacitor feedback waveform 

Just turning on with a rail voltage of 0.79 volts

'Well on' rail voltage is 1.02 volts.