RSGB CW National Field Day. Frequently Asked Questions

Please note -- there is a selection of diagrams to explain some of the potential antenna configurations
      in the Restricted and Low Power Sections, also showing maximum permitted height in the Open Section.

(Q1) Why are there so many questions and answers here?

Because the Contest Committee wants entrants to understand the thinking behind the changes to the NFD rules. It is important for entrants to realise that if they wish to they can continue to enter Field Day almost exactly as in previous years.

(Q2) Why have the Restricted and Low Power section rules on antennas been changed? Please explain in simple terms how the new rules differ from the previous ones

The previous rules allowed a single element antenna with a maximum of two elevated support points and a maximum height of 11m. FD entrants have commented that this placed major limitations on the type of antenna that could be used. The new rules have been designed to offer increased flexibility, thereby allowing entrants more scope for innovation & experimentation, but without a significant increase in resources being required. Condensed into a single sentence, we are saying "You can have up to 120m of wire and a total antenna support allowance of 22m, and you can do almost what you like with it". Thus an entrant could choose to use two masts at 11m (as per the previous rules), four 5.5m masts (which would, for example, permit use of a horizontal loop), or any other combination up to 22m in total. Note, however, that that under rules 4c & 4d any structural supports within the antennas themselves (eg. booms or spreaders) contribute to the antenna support usage -- see later for examples. Under these new rules, the antennas supported by the chosen arrangement of mastage could be of any type or number within the overall antenna length allowance of 120m.

(Q3) Is it really as simple as that? For example are there any limits on what can be used as antenna supports?

There are a few constraints, some of which have been carried forward from the previous rules. The principle here is "empty site to empty site". Any structures erected during the 24 hour pre-contest period (eg. scaffolding masts, towers) remain acceptable. Permanent man-made structures may not be used to support antennas, but trees are acceptable. Note that the total height of each supporting structure (eg. mast or tree) is not relevant -- it is the height from which the antenna is supported that contributes to the antenna support usage. Some further constraints have had to be applied, mainly to prevent overlap between antenna capabilities in different sections. These are set out in the rules and these FAQs. In order to demonstrate how the principles are intended to operate, the associated diagrams give examples of how a number of typical mastage configurations would contribute to the antenna support usage.

(Q4) Given that there is a 22m antenna support allowance, why are we limited to a maximum antenna height of 15m?

In addition to helping to maintain a distinction between the Open and Restricted / Low Power sections, concerns had been expressed that erecting a 22m mast would present too much of a challenge for smaller clubs. Therefore to avoid such clubs being disadvantaged, a maximum antenna height of 15m has been put in place. The combination of 22m antenna support allowance and maximum antenna height of 15m permits the use of multiple masts and maintains considerable scope for experimentation.

(Q5) Are we still constrained to using a single antenna?

No. As stated above, you can use as many antennas as you choose within the overall antenna length allowance of 120m.

(Q6) In different parts of the rules and FAQs, you use the terms "allowance" and "usage" in relation to of antenna supports and antenna lengths. Are these alternative terms for the same thing?

No. The allowance is the maximum the rules allow you to use (i.e. 22m for antenna support and 120m for antenna length). The term "usage" applies to what your FD setup actually uses. So if your antenna setup consisted of 3 doublets of lengths 78m, 19m & 11m, your antenna length usage would be 108m.

(Q7) Why must I make Restricted and Low Power section antennas out of wire? Why can't I use tubing?

That statement isn't quite correct. Antennas do not have to be made out of wire in the following cases:

(Q8) Does that mean we are not allowed to use beams in the Restricted & Low Power sections?

No: beams are permitted in these sections, since their prohibition would reduce the scope for innovation & experimentation. However, the rules regarding the use of wire elements apply. Thus, for example, a cubical quad would be acceptable, as would a Yagi made from wire attached to rigid spreaders. But it should be noted that any rigid supports which form part of the antennas would contribute to the antenna support usage.

(Q9) Does the overall antenna length allowance relate only to driven elements?

No: it includes all the antenna elements. For example, if you chose to build a parasitic beam for 40m, the length of the parasitic element(s) would contribute to the overall antenna length usage. Any elevated radials or counterpoise elements would count towards the total antenna length usage, but radials laid on the ground would not.

(Q10) Hold on a minute! We're using scaffolding masts to hold up our antennas. Inevitably there will be some small degree of parasitic radiation from the mastage. Surely that doesn't mean that the mastage must count towards the overall antenna length usage?

No, provided radiation from the mastage is not an intended or significant part of the antenna system design.

(Q11) I'm not quite clear how verticals would contribute to antenna support and antenna length usage -- can you clarify please?

The following text and associated diagrams should make this clear:

(Q12) Once we've got our wizzo new antenna setup in place, are we allowed to change it during the contest?

For a number of years, some groups have been reducing the length of their doublet (usually by pullable links) once activity on 160m has ceased. This approach is specifically allowed by the new rules. So changing antennas during the contest is permitted, provided that all the antennas used during the contest have been constructed from within the overall antenna length allowance. Thus it would not be acceptable to take down a 100m long doublet and replace it with a separate 50m long doublet (as that, at 150m, would exceed the total antenna length allowance), but shortening an existing 100m doublet to 50m length would be acceptable.

(Q13) Are we allowed to use traps?

Yes. Devices such as traps, loading coils, stubs and phasing lines may be used to change the electrical length of any antenna. Relay switching and mechanical links are also permitted.

(Q14) Do such devices contribute to the antenna length allowance?

No: neither do feeder lengths

(Q15) Our club has always used a dipole at 11m. Do the new rules mean that we will have to abandon it?

Not at all. The new rules have been specifically designed so that the traditional "NFD doublet" and two 11m masts can continue to be used, and it will continue to work well.

(Q16) Why have the site rules been changed?

The underlying principle behind Field Days remains "empty site to empty site", in which entrants typically transport all their equipment to an empty (typically rural) site just before the contest, set it up, operate the contest, take it down and leave the site. However, in recent years there have been changes in the type of sites used by entrants. In additional to the traditional type of site just described, we now see (amongst others):

It is expected that the requirement for transportation of equipment will present no problems for the majority of entrants. However circumstances may arise, typically in case (c) above rather than cases (a) & (b), and perhaps due to causes such as physical infirmity, where compliance with this requirement results in particular difficulties. In such circumstances entrants may ask the Contest Committee for a ruling as to whether the spirit of the rules would nevertheless be observed in an exceptional case, so that a dispensation could be given.

(Q17) Does the requirement to transport equipment across the site boundary relate to just "radio equipment" (i.e. what is directly used to enable operation of the station in the contest) or are welfare / catering facilities included?

For 2012 at least, the requirement applies only to the former.

(Q18) I'm glad to see that the 24 hour setup period has been retained, but why has the 32 hour period been introduced?

This is to provide a time window in which equipment that has to be removed from, and returned to, site in accordance with Rule 3 can be moved without using up part of the 24 hour setup period. Allowing a 32 hour period permits the movement of equipment shortly in advance, but prevents such movement taking place days or weeks in advance of the setup period.

(Q19) Why have the new rules regarding CW skimmer and public internet based services such as RBN been introduced?

The Contest Committee considered the use of RBN & CW Skimmer as part of its brief to keep an eye on new technologies and assess their suitability for introduction in RSGB contests. It concluded that permitting RBN, along with other public internet based services such as DX Cluster, in Field Days would have a negative impact, as:

(Q20) The rules seem to talk about use of CW Skimmer in 2 different ways -- can you please clarify?

In the Open section only, the full capabilities of CW Skimmer are permitted as an aid to finding contacts.

Quite separately, and in all sections, the use of CW readers such as MixW (which use CW Skimmer-like technology) is being permitted in order to enable operators who cannot read CW to participate in Field Day. In this case, in order to make the operating conditions as similar as possible to those experienced by an operator using brainpower to read CW, no additional receiver is permitted and the bandwidth used is limited to a maximum of 3kHz, which must always be the same frequency range that the operator can hear. There must also be no connection between the CW reader and the contest logging software: callsigns and serial numbers must still be typed in by hand. The Contest Committee believes that use of CW readers in this deliberately limited way will offer no competitive advantage over a competent human operator, while helping non CW-literate operators to make a start in Morse Code and providing the incentive to progress to traditional "brain powered" CW operating.

(Q21) Why have the rules relating to rigs been changed?

For a number of years, transceivers with a second receiver have been permitted in Field Day as a means of seeking additional contacts (the so called "big knob, little knob" mode of operating). Capabilities offered by most modern logging programs and the use of networked computers now offer additional, more flexible, means of achieving the same end. In particular, traditional "big knob, little knob" operating requires the main and spotting operators to sit in front of the same transceiver which can be rather cramped (and arguably impossible with the increasingly popular but physically small K3 transceiver). Also with traditional "big knob, little knob" operating the ability to have the spotting operator on a different band to the main operator is only possible with top end transceivers not available to all entrants. On the other hand almost all groups will have access to two or more ordinary transceivers.

The rules for all sections have therefore been changed to allow 2 transmitters provided only one signal is transmitted at a time. This has the advantages of (a) making dual receiver operation more convenient ergonomically, and (b) allowing the main and spotting operators to be on different bands without the need to use of top end transceivers: the ability to now use multiple antennas in the Restricted and Low Power sections makes that a more important consideration than hitherto.

Most modern logging programs support the "2 transmitter, 1 signal" approach by (a) allowing a single log to be shared between 2 networked computers, and (b) providing interlocking so that stored messages on one computer cannot be transmitted at the same time as stored messages on the other. However such interlocking does not prevent hand keyed CW being transmitted by one transmitter at the same time as stored messages by the other. Therefore hardware interlocking is required to prevent simultaneous transmission. A hardware based approach is in any case required to provide receiver protection and, where appropriate, to implement antenna switching.

The number of receivers permitted has (with the exception of an extra receiver in the Open section to support CW Skimmer) been limited to two. Without this limitation, a 2 transceiver setup could support up to 4 receivers, thereby allowing one main operator and up to three spotting operators. This could only be effectively utilised by the very largest clubs and would place the majority of (frequently resource-constrained) groups at a disadvantage: therefore the number of receivers has been limited to two.

(Q22) Why is there a "muting" requirement in the rig rules for the Restricted and Low Power sections which does not apply to the Open section?

The full capabilities enabled by operating in "2 transmitter, 1 signal" mode require the use of complex arrangements involving bandpass filters and triplexers, and it is felt that these advanced capabilities are available to relatively few groups. Therefore while such full capability operation is permitted in the Open Section, for the Restricted and Low Power Sections, it is required that both receivers are muted when either transmitter is on transmit. This might be achieved, for example, by short circuiting the receiver inputs.

The effect is that (a) the mode of operation becomes similar to the traditional "big knob, little knob" system while allowing increased flexibility, and (b) the distinction between Open & Restricted / Low Power sections is maintained.

Entrants will need to design & implement their own arrangements for ensuring compliance with the rig rules based on the configuration of their particular stations (and may be required to demonstrate to an inspector how that compliance is achieved). The Contest Committee recommends that entrants should consider the need for protection of receiver front ends from the presence of RF from the "other" transmitter as part of their design.

However, an example of a basic circuit which could be customised for individual setups is included in the diagrams.