Clublog

Spiderbeam

Elecraft

M0OXO

Microham

FOC

Equipment

We have planned for three separate stations at 9G5X, all to be set up inside a single operating room within the main hotel building. Each station will be identical, with an Elecraft K3/100 transceiver and a matching Elecraft KPA-500 500W linear amplifier. All our K3/100 radios are fitted with the latest KSYN3A synthesizers, producing cleaner synthesized signals, in turn leading to better transmitter and receiver performance and less inter-station QRM. The new KSYN3A has faster switching times to improve TX/RX switching for high speed CW, avoiding problems with keying distortion in split frequency mode and allowing proper RIT operation on receive.

K3

An Elecraft K2/100 will also be available as a stand-by, or as operator preference dictates, to be used instead of one of the K3/100 transceivers. There is still much debate about the effectiveness of the Elecraft K3 receiver under heavy pile-up conditions. We found at C5X there was no problem in this respect, provided careful adjustment was made to the K3 receiver AGC. The factory AGC settings are not suitable for pile-up conditions and produce distorted 'mushy' audio in a heavy pile-up.

Single band 5B4AGN TX bandpass filters will be fitted between each K3 and each KPA-500 to provide increased isolation from adjacent band overload. Although Elecraft K3 radios have very clean RF synthesizers, additional filtering, provided by the TXBPF at the output of the transceiver, reduces transmitter synthesizer hash even more. In addition, we will have a number of single-band 500W filters fitted on the outputs of the KPA-500 linear amplifiers to prevent reverse SWR damage with mutually coupled antennas, e.g. when both Spiderbeams are in use. We are aware that on some expeditions there have been failures to the T/R switch in the KPA-500 PA block, probably caused by RF mutually coupled into the antenna. These 500W filters are designed to mitigate against any such problems.

Antennas
We are taking a 3-Band Spiderbeam and a 5-Band Spiderbeam to be rigged on the roof of the main hotel building at a height of about 15m to 20m a.g.l. In addition, we will have a 2-Band Moxon beam for 17m and 12m on a 12.5m Spidermast.

On 40m and 30m, we will have separate dipoles on the roof of the hotel at a height of 20m a.g.l. All our antennas will use Aircell 5 coaxial cable, which is lightweight, relatively low-loss and easy to carry.

Spiderbeam

Above: Spiderbeam supported by a ladder at A25/DL7DF, Botswana 2008.

3-Band Spiderbeam
 
5-Band Spiderbeam

20m

15m

10m

 

20m

17m

15m

12m

10m

Number of Elements

3

3

4

 

3

2

3

2

4

Forward Gain
at 10m height [dBi]
11.7
12.3
12.6
 
11.7
10.5
12.3 
10.5 
12.6
Front/Back ratio [dB]
15-20
20-25
20-25
 
15-20
20-25
20-25
10-12
18-22

SWR

< 1.5
< 1.5
< 2
 
< 1.5
< 1.5
< 2
< 1.5
< 2
Max. Power
2000 W  /  balun is included
 
2000 W  /  balun is included
Impedance
50 Ohms  /  single feedline
 
50 Ohms  /  single feedline
Boom length
10m  (33 ft)
 
10m  (33 ft)
Turning Radius
5m  (16 ft)
 
5m  (16 ft)
Wind load area
0.35 sq-m  (3.8 sq-ft)
 
0.35 sq-m  (3.8 sq-ft)
Weight
6.7kg  (14 lbs)
 
7.5kg  (16 lbs)
Transport Size
120x27x18cm  (47x11x7 inch)
 
120x27x18cm  (47x11x7 inch)

For the L.F. bands, we shall be using two 18m Spiderpoles to support 160m and 80m verticals, similar to the array pictured below.

Spiderpole Vertical

Above: Recommended 160m and 80m vertical array, but in our case we shall be using two separate 18m Spiderpoles, one for each band, to reduce mutual QRM. Verticals are noisy on receive and to help with weak signal reception on 80m and 160m, we will have two 600ft Beverage receiving antennas.

Logging
For DXpedition logging, we are using the latest version of N1MM+ contest logger in DXpedition mode. Three Lenovo laptop PCs will be networked with a TP-Link wireless router, each running a copy of N1MM+ to allow us to run three stations simultaneously if band openings allow. The router will have a 3G USB wireless adapter to give us Internet access for uploading logs to our QSL Manager, Charles M0OXO.

N1MM+